Jakolito

Hello! I am currently running this campaign for a group and they have just had their meeting with Miss. Carlyle and gotten to see the books contained in the safe. One of the players are quite wealthy and another one owns a university. The players want to buy the books of Miss Carlyle, which propably should be possible if they put their resources together with some of the money that Jackson Elias left behind for them. Miss, Carlyle told them that she was gonna have the appraised and get back to them. My question is; since these books are quite rare what would be an appropriate amount for them? Is there any rules in CoC7 that I overlooked that can help me calculate this? Has anyone else had the same scenario with a group of players and what did you put them at? Thanks ahead of time!