Buying an expensive bass cured me. I've always bought cheap instruments, but have always GAS'd for something better. I finally bit the bullet and bought a Dingwall ABZ used on the classifieds here. It's honestly spoiled my desire for cheap basses... while I love some of them, this bass has taught me that saving and getting what I really want can be rewarding. It didn't require any work, any effort, nothing to be playable and amazing sounding.
I have 20+ instruments... 4 guitars (one in pieces), 1 mandolin, the rest basses. I can see myself now getting down to 9. From a utilitarian standpoint, I only really need three of the basses (Dingwall, fretless, U-bass), but there are others that I'm keeping for sentimental reasons (ones a rare color, one is my first project undertaken with my wife, and the T-40 is the one I've had the longest).
GAS is a killer. I think I've cured mine... at least for basses, now I'm thinking of upgrading my amp head.