I think for the general public this is a reasonable comparison, since the performance is good enough for most things on a 2 year old eng pc for less than half the msrp. I would expect most corporate refurbs on eBay to be moderately reputable, and eBay is know to be consumer friendly.
I would consider buying a used computer from a person, if I could test it in advance. I don't think I'd ever buy a computer sight-unseen off ebay. They may be customer friendly on balance, but they're unpredictable enough that I wouldn't want to spend that kind of cash and risk being completely screwed.
