the cover doesn't look completely split to me? Looks like it has some splitting there below the bottom staple. If you are considering it detached and even partially split, along with the other issues and overall look of the book I'd agree with 1.5 or so. It presents decently well, there aren't any pieces missing or big rips or super ugly flaws.
As for price, I don't think 5,500 is crazy to ask for this copy based on the market right now. But it seems a little like you are asking us to talk you into buying it, and that's a troubling feeling.
IMO, it's better to not have a big book that I'm unhappy with just for the sake of having it.
If that isn't the case, if this is the book for you and you wanna have it for a long time, then go for it!