I purchase mostly NGC graded Morgan dollars, all MS 60-MS65. Every now and then I will buy PGGS graded Morgan Dollars, again, all MS 60-MS 65. Currently, I am flirting with the idea to buy a NTC graded Morgan dollar and then send it to NGC. Then come back to this forum and post the results. I have not been 'burned' on E-bay (yet) where I did not recieve product. The only raw coin I purchased, I sent in to NGC and it came back three grades lower than I thought. It was a Lafayette dollar. As a consequence, I do not ever purchase raw coins from E-bay. I learned my lesson.
Before I use ebay I decide what I will pay for an auction coin(I check local dealer, search some on-line sites, etc.). Yeah - I have lost more than I won, but so far I think I have done okay. My best buys are $183 for 1998,1999,2000 pcgs pr69 dcam silver eagles and $41.10 for a 1988 pcgs pr69 dcam coin. These prices include insurance and s&h. SO far no problems with ebay sellors or the coins. What I am trying to figure out about ebay is (1) Why do people bid more than a buy it now price and (2) bid on one auction while another goes un-noticed. Yes - I understand about feedback and such, but I bought a 2002 proof eagle for $31 including s&h while a couple of auctions still were running with higher bids(including s&h). I still have not figured out why I was the only bidder.
I use Ebay to buy bullion coins at bullion prices. I'd hesitate to buy slabbed coins because the photos could be deceptive in judging the eye appeal. I'd never bid on a raw coin.
I buy raw Kennedy proof coins a lot. I have never been disappointed with any coin that I have bought. Proofs are flawless and I expect them to be perfect when they arrive. I've filled one coin book full with proofs I purchased on ebay. Even after mail costs they are cheaper than the local coin store.