eBay used to be great for genuine deals. I wheeled and dealed my way through three different bike builds about six years ago. Much depends on the quality of a listing and I would often take chances on poorly advertised parts and resell them with good pictures and clear, concise description, typically for a relatively good profit.
It's a kicker when your stuff goes for cheap, though. I had a once-used e13 chainring go for £1.24. The kid I sold it to actually apologised, although his bid had been for £15, and asked if I still wanted to sell. Like you say, it's (sometimes!) nice to give somebody a bargain – there's one waiting for you out there, for sure…
