eBay
is pot luck for LPs. You never know what you're getting. Almost no one play grades, all are done visually, so a grading unless it's bad, has not a lot of relevance to how good it sounds.
I only buy on eBay from, a known source, a sealed disc either NOS or re-issue or get them very cheap.
A known source is the hardest to find. I bought an LP this week off a guy who posts on AA a lot and has very fine gear and taste. I knew it was him because I recall someone asking about an auction of his a while back and made a note of his moniker. The disc is extraordinarily good. Not cheap but good value.
About a year back I bought an MFSL of a guy who turned out to be local. I went and picked it up, we spoke for hours and I took away about 20 more discs. He knows I want mint only, so I send him a list and he mails them to me (I now live 1000km away) and I send him the money when I check them, mainly because he will add in a few others he thinks I might like, though if I'm not happy with any, I just send em on back. Best way to buy LPs I've ever had.
It took luck and a good memory to find both these guys (plus others I know). And patience. The trick with eBay is patience and being willing to let the deal go, and look for the next. If it feels bad, or you have any reservation about it AT ALL, or the price is escalating in a bidding war, or you suspect a shill, walk away, it's not worth the greif. And remember, except for a few audiogeeks no one cares about the discs absolute sound quality. Can you hear the music?
Sealed discs are easy, just check they're feedback and maybe ask them some questions, like are they cutouts and where did they source them. For a high $ disc, I email previous customers and ask them about the quality of the disc and the transaction.
Cheap stuff are discs I'm prepared to write off the $ on even if they're total duds. No bad ones yet.
All that said, I've bought one really bad disc out of over 100. It was graded M/M, packed exceptionally well (disc outside sleeve, custom reinforced mailer, padding) and was a rare title I wanted and cost a lot. It looked exactly as described, the guy was a pro from his packing, knowledge and attitude but............it must have been played with an old nail, so bad did it sound. The seller was very good, explaining his grading was visual, gave me the website for his long established store and offered a refund. He is in the US, so it wasn't worth the cost to send it back. He also uses a cheapo plastic fantastic to play his LPs on, so a play grade would have been worthless anyway. Eventually I sold it on cheaply to a friend who loves it.
Good luck.
). Oops, forgot, 
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.. <vbg>
their grading is, you don't risk much. 
