In terms of market demand, which option is most indicative of ruby prices?

Focusing on the factors that specifically indicate ruby prices, color saturation and size are indeed the most significant determinants in the marketplace. In the gem trade, the most sought-after rubies exhibit a vivid red color, referred to as "pigeon blood," which directly influences their desirability and value. Larger stones in this optimal color range command a premium, as rarer gems are more valuable.

While inclusion levels and clarity also play a role in determining a ruby's value, they are not as significant as color and size when it comes to market demand. Similarly, although shape and origin can affect a gem's appeal, the overwhelming focus on color saturation and size is what truly drives ruby prices upwards. Thus, prioritizing color and size makes sense when evaluating ruby prices in the market.