I like the concept, if only as a feedback mechanism to one's own buying habits. (Which are, in my case, deplorable!) The catch is, I don't currently keep track of the source of where I got my books and how much I spent on them. True, it's somewhat easy, in that >90% of them are from either Baen or Amazon. And the Baen books (except for eARCs) will never be "the most expensive", even with the new pricing structure. But some books I get from Kobo, and some others from the Library. And I really don't know which are which.
Realistically, I don't see myself changing to be that organized about tracking my books. Just not going to happen.
