I sold my A500 for £40 about 2 years ago... Well, it was more cobbled together. I found one at the dump, complete in the box... gave the dude a 4-pack of beer to look the other way. The disk drive was knackered, but I had several around anyways. Cleaned er up, sorted out a few cold looking solder joints, looked nice. I used it for a few months and hocked it.
I guess it all depends on condition and the right time.