The golden guess is the morning-star to the full round of truth.
Lord Alfred Tennyson [1809–1892], Columbus
WHAT'S THE PRICE? That is the question on everyone's lips. Unfortunately, the answer seems only to spring from the lips of the seller. 
Lack of a universally-accepted system of quality analysis and the numerous non-quality factors which can affect price make it extremely difficult to come up with logical price tables for ruby and sapphire. But difficult does not equal impossible. In an attempt to bring ruby and sapphire pricing in from the cold, the author, together with Donald A. Palmieri of Palmieri's GAA Market Monitor,  has compiled the following tables. Consider this a brave attempt at bringing order to chaos. And when you find inconsistencies and mistakes, just remember that old saying about how you can tell the pioneers by the arrows in their backs.
Market memos – May, 1995
Burma (Mogok & Mong Hsu). Mogok rubies continue to bring top prices in the wholesale trade and at auction. There is an ample supply of heat-treated commercial stones, but most of these originate from the Mong Hsu area, not Mogok. Approximately 70–75% of the better-quality Mogok rubies going through certification reveal either low temperature heat or no evidence of heat treatment at all. According to the markets monitored, there is no difference in value for these categories. Of the 25–30% heated to high temperatures, most will sell for up to a 40% discount below the price for the untreated and low temperature heated stones.
Thailand/Cambodia. More than 99% of all Thai/Cambodian rubies have been subjected to high-temperature heat treatment. Fine goods are scarce and Far East demand continues to put upward pressure on prices. Many fine goods remain in the inventories of American dealers.
Kashmir. As more heat-treated Kashmir sapphires are found in the market, the question of value differences between heated and unheated Kashmir stones becomes ever-more important. Fine Kashmir sapphires are distinctive in color, texture and inclusions and so can often be positively identified as to country of origin. Heat-treatment makes origin determination more difficult, with heated Sri Lankan stones being confused with Kashmir, and vice versa. Extreme caution is recommended when buying, selling or appraising. Market values listed are for untreated stones only. Some dealers will charge the same for a treated stone, and some discount a treated stone up to 30–40%. One thing is certain – a dealer will not pay as much for a treated Kashmir sapphire.
Burma (Mogok). Supplies of Mogok sapphires are as tight as for Mogok rubies. There is little fine material around. Prices are relatively stable, and those who deal in better sapphires buy all they can. Mogok sapphires are being heat treated with increasing frequency. Like their ruby cousins, heat-treated Mogok sapphires are worth less than unheated stones.
Sri Lanka. Today, most Sri Lankan sapphires have been heat treated to improve their color. From about 1975–1985, the market heat treated stocks of geuda sapphire which had built up over the centuries. These stocks are now depleted. In addition, heavy rainfall in the early 1990s also hurt production. While mining is today proceeding normally, little fine material is available. In historical terms, this is the normal state of affairs for sapphire mining in Sri Lanka. Thus, barring development of new treatments/new mines, we cannot expect to see the availability of Sri Lankan sapphire ever again reach the levels of the early 1980s.
Other blue sapphire sources. This includes sapphires from many localities, including Australia, Thailand, Cambodia, Laos, Nigeria, China, etc. Virtually all sapphires from these sources have been heat treated. Stones from these sources tend to be iron-rich, and of darker, inky-blue colors. Thus they are of lower value than the better stones from Kashmir, Burma and Sri Lanka. Many stones found in investment and barter scams come from these sources. But keep in mind that good and bad come from every mine. A small quantity of fine sapphires are found in Australia, and it would be far better to have a fine Australian sapphire than a poor piece from Kashmir or Burma.
The term fancy sapphire is used to describe corundums other than red or blue. When it comes to fancy sapphires, Sri Lanka is king of the hill. Within this small island are found sapphires of virtually every color, including some for which the island is the definitive source (such as the lovely pink-orange padparadscha). Tanzania's Umba Valley is also noted for fancy sapphires, as are Montana's non-Yogo mines. But again, Sri Lanka is King, with a capital K. The sizes and colors found on that island are enough to make any Montana or Tanzanian miner cry uncle.
Yellow & orange sapphire. Yellow sapphires from Sri Lanka are generally of a light to medium hue, without any brownish overtones. Like Sri Lankan blues, deeper hues are reached only in larger sizes, or via heat treatment. Heat treatment produces deeper yellows, golds and oranges that are virtually unknown, or rare in nature. The very rare pinkish orange padparadscha sapphire is found mainly in Sri Lanka and at Vietnam's Quy Chau mines. While similar gems are sometimes found at Tanzania's Umba mines, most from this locality tend towards the brownish orange. Padparadschas from Sri Lanka sometimes fetch prices that rival even ruby.
Thailand and Australia both produce fine yellow sapphires, with the stones from Chanthaburi in Thailand grading into the highly desirable Mekong Whisky golden yellow to orange colors. These bring high prices locally in Thailand and are quite beautiful. Australian yellow sapphires tend to be overly greenish, although fine golden yellows are found in the Anakie, Queensland mines. Sri Lanka, Thailand and Australia are the only sources which produce deep yellow sapphires in any quantity, although Montana and the Mogok area produces the occasional stone.
Green sapphire. The finest green sapphires come from Sri Lanka, but are extremely rare. These stones tend to be of a lighter and more lively green than the Fe-rich stones from Thailand and Australia. The latter two countries do produce good green sapphires, but most tend towards an impure blue-green or yellow-green which is not very attractive. Green sapphires of good color and clarity over 10 ct in size are relatively scarce.
Violet and purple sapphire. Violet and purple sapphires are found mostly in places which produce both ruby and blue sapphire. The finest stones come from Mogok, Sri Lanka and Vietnam. Purple stones bordering on ruby color are most valuable and may reach prices approaching those of ruby. Star stones are possible, but relatively rare.
Color-changing sapphire. Among the most unusual sapphires are those which display a change of color. These are judged by the quality of color change, the best ranging from the green side of blue in daylight to a reddish purple in incandescent light. A number of sources produce such stones, but fine examples are rare. The best are colored by vanadium (just like the Verneuil synthetic corundums) and come from Mogok and Umba, Tanzania. These are extremely rare. More common are Sri Lankan gems which contain a mixture of chromium (red) and iron-titanium (blue). Such stones appear bluish violet in daylight and purple under incandescent light. In the author's opinion, these are marginal as color-change sapphires. Most tanzanite shows a similar color shift.
Star stones & cabochons
Prices of star stones and cabochons are generally slightly lower than their faceted brethren of the same quality, but may approach those of faceted stones in the highest qualities. Good quality stars and cabochons must display fine transparency and color (see 'Judging stars & cabochons', p. 222).
Virtually all rubies and sapphires sold today have been subjected to high-temperature heat treatment for color and/or clarity enhancement (the exception is stones mined prior to 1975 and not subsequently treated). Today, it is the rare stone which has not been heat treated. Telltale signs of this treatment can often be found by experienced gemologists (see page 116). Market values for Thai/Cambodian rubies and most sapphires are based on the assumption that all have been heat treated. Conversely, market values for Mogok rubies and blue sapphires and Kashmir blue sapphires are based on positive gemological proof of country of origin and no detectable trace of any treatment (beyond ordinary cutting and polishing). Flux-healed rubies are showing up more frequently than in the past, particularly from Möng Hsu (Burma). For blue stones, be aware of surface-diffusion treatments. While experienced gemologists can easily identify this material (via magnification and immersion), it can fool the unwary. Also be aware of synthetic corundums treated by the surface-diffusion process (synthetic colorless sapphire is far cheaper than naturally-mined material).
The buying, selling and appraising of rubies and sapphires must be undertaken with the utmost care and caution. Know what you are buying and from who you are buying. Ask about treatments, heat, fracture-filling and otherwise. It may not be important to you until your client finds out from another jeweler or appraiser that the ruby he/she purchased from you has glass-filled cavities. According to the law, ignorance is no excuse. When selling, fully disclose everything, including things you take for granted that a judge or consumer affairs reporter would interpret as misrepresentation (even if by omission). When appraising, never identify a stone unless positive evidence is found. If doubt exists, get a second opinion locally or obtain your client's permission to send it to a competent lab for further analysis. This goes for natural vs. synthetic, treated vs. untreated and/or country of origin. The appraisal fee is never high enough to risk one's integrity and reputation on a brief moment of misjudgment. In summary, report everything you would want to know if you were purchasing the gem.
Categories represent broad, integrated quality grades, based on a combination of color, clarity and cutting quality.
Table B.1: Ruby (including pink) prices – cut stones
* Note: Due to their lack of fluorescence and light-scattering silk inclusions, Thai/Cambodian rubies will rarely fall into the exceptional category.
Table B.2: Blue sapphire prices – cut stones
Table B.3: Fancy sapphire prices – cut stones
This page is http://www.ruby-sapphire.com/r-s-bk-prices.htm
Page updated 7 March, 2013