Granted, I am not on there buying expensive, rare, or collectable items that lend themselves to fraud.
I have had some incredible buys though. I got a China Cap (A giant stainless steel strainer) for $10 that retails from $80-100.
I buy my wife the "This Little Piggy" figurines for between $4 and $8 and they sell in the store for $25. And I got her the entire "Wedding" set for $26, and that has 10 pieces in it and retails for over $150!
My biggest score so far though has been a NADY wireless system for my guitar. For years I tried to find a used one cheap. But they were always $100 and up. I got mine for $56 delivered to my door, and the seller, as a surprise put a bag of pretzels from a local specialty shop in the box. And they were some of the best pretzels I have ever had.
eBay is great for finding things that you can not find anywhere else. If you want it, its on eBay.