I'm curious Bonknuts...how did you end up paying $230 for Macross 2036?
Anyway, I've sold a few things over the years that I regretted later. Beginning with my original NES and about a dozen games. I sold them to afford the Turbografx-16. Now I don't regret buying the Turbo, but I wish I could have done it in some other way than giving up my NES.
Around 1999 I sold off some Saturn games that later got rather valuable (Astra Superstars and Phantasy Star Collection are two that I can remember). I was able to buy them back a few years later, but not nearly in as nice condition as the ones I sold.
The biggest regret I have is selling off almost my entire Nintendo 64 collection a couple years ago when I went through one of those "oh, I'm too old for videogames, why do I waste time/space with all this crap" phases. I had a collection of about thirty games, all purchased new by me and absolutely pristine (I'm very, very picky about taking care of my stuff, and everything I've bought since the mid-80s has been kept in mint condition). But as I said I was going through one of those silly (in retrospect) "I need to grow up" phases, and I sold all of them except for Ogre Battle 64 and Paper Mario, which I kept because I had not finished them yet. Even though I abhor the N64 controller and the blurry N64 graphics haven't aged well, I miss some of those games terribly. I've scanned eBay occasionally with the idea of buying some of them back, but I know I'm unlikely to ever get them in the same condition as the ones I sold off. The chance to play games like F-Zero X and Starfox 64 again is about the only reason I'm slightly interested in the Wii (for the VC).