If I had really need it I would probably have topped out at $400, if it was really clean, had drawer liners and the keys to go with it. I like the bottom box, but not the top. Anymore than that and I could get a 44" HF (better quality considered by some) brand new top and bottom for slightly more.
On the selling side I probably would list it at $525 and expect to take $400-500, again depending on the in person condition. I think you got around top dollar for that box. Craftsman boxes have the highest resale value % of new than any other box manufacture. I contribute that to the fact craftsman is a household name.
EDIT, used box values can be very regional and competitive with the local market.