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.
My most expensive (though much, much less than buying from a retailer) and exotic item I bought through eBay was a neon bar sign for my sister and her husband for their rec-room. When my daughter had her First Communion last year I went through the eBay stores and bought a beautiful dress and veil (separately, from separate vendors) and saved much $$$. These and all of my other purchases have been exactly as represented and it is a delight to use.