It's a great idea but it would never work because the prices on BPs fluctuate so much. Some people will try to sell their animals as cheap as possible just to get rid of them while others wait to get what they think their animal is worth.
Additionally, there would have to be a "clarity" scale like they have for dimonds because price usually depends on quality of the animal. Also it depends if it's a male or a female, what they weight is, and if they're proven or not. It's just too many variables.