The thing with an RPG is that you can track prices due to the fact that it all happens in a game, and it's easy to locate how much a marketplace value is. With the ball pythons it's all through classifieds, breeders, and shows, which would be nigh impossible to put that all into one place. Plus quality and such plays in. A pastel is usually between $75 (low quality males) up to $400 for an animal that stands out.
More than a tall order, and definitely more work than anyone wants to do for very little gain. It's better to look around and expect to pay good money for morphs that stand out. You can get a good idea of what you'll pay by looking through kingsnake.com or breeder websites