I'm pretty sure I've seen this cognitive bias described in the literature, but I can't find its official name, so I'll provisionally call it "the used-book finder's bias", based on the following vignette.
Say you are browsing through some used-book store, looking for nothing in particular, when you spot, tucked in some corner, almost hidden, a copy of some "classic" book. The book is in good shape, and the price is very attractive. What a find! You've got to have it, never mind the little voice reminding you that your reading list is already overcrowded, as are your bookshelves, and that you won't have time to read this book in the foreseeable future...
The cognitive bias I'm referring to is the intense compulsion to acquire the serendipitous find, even though one does not need it, and almost certainly will not do anything with it.
As someone who used to frequent used-book shops, I'm all too familiar with this cognitive bias. It led me to spend a lot of money, and acquire more books than I could even store, let alone read. (Eventually, I wised up.)
Mind you, the vast majority of the books I found this way were not really hard-to-find; I could easily get through other means (e.g. the library) if I ever really needed to read them. Moreover, if I had just paid full price for brand new copies of the very few among those books that I ultimately read, I would have still saved myself a lot of money.
The principal element of the bias, seems to me, is the strong feeling of good fortune one feels in such a situation. Conversely, one feels strongly that one would be a complete fool not to take advantage of such a lucky event.