Just as a counter. You are not obligate to listen to OP's comment, that is just one of the many perspectives that one can have around a book shopping.

Please go ahead and do build a hyper focused product which finds out most 'inexpensive' source for a book that one is clear about (that is, one is not in a discovery mode).

I'm sure there would be whole lot of students who would be super thankful about this service, there is enough of price gouging in educational segment. Even if you are not building textbook related service, still it would help.