Sapphires are all about color and this makes it the most important factor when it comes to value. Other factors are carat, inclusions, transparancy, cut, signs of treatment(s) and color saturation.

Sapphires are more commonly found with less inclusions then rubies or emeralds but inclusion free sapphires are still rare. This still means that inclusions have an impact on the value of a sapphire there are just more sapphires with not that many inclusions. One type of inclusion might have a positive out come towards value and that is silk a very subtile form of rutile needles. It also causes the asterism effect in cabuchon cut sapphires. 

Heating is one of the main treatments sapphires undergo and is mainly done to bring out the gemstones color. It does have a serious impact on the value by almost cutting it in half. Heating with residue leaves the price at a third of a natural untreated sapphire and other treatments like cobalt lead glass filling make the sapphire practically worthless.

Sapphires are found in many different colors, those that aren't blue are called fancy sapphires. Fancy sapphire colors are green, orange, pink, purple and yellow. There is also a combination of pink and orange called padparadscha. This form is very strictly bond to a certain hue in colors that range from light to medium pinkish orange to orange-pink. Padparadscha sapphires are very rare and accordingly very valuable.