It totally depends on the coin and the market. I know of many times I and others pay way over a listed price because we know the "particular coin" is extremely rare or hardly ever comes up for sale, or in a condition not often seen, or if we have a buyer in line for a profit regardless of the price.
As to market price to a retail customer, a wholesaler or a dealer is always a variable. But generally I see coins like common better grade Morgan &
Peace dollars, and semi key silver coins sellers asking for at least $50.00 over PCGS Price on
ebay site, I think Teletrade price realized and Heritage Auctions are the truest prices, dealers like to pay 10% back or more from bid in greysheet when buying, but again it will depend on the coin.
I'd gladly pay over ask for a super nice 1864LM Proof
Two Cent Piece, but I would not pay bid for a MS-65 or less example, the difference is how often I can get one, 1864LM in MS65 are easy, try finding a Proof 1864LM in any grade, it's tough. I've only seen 8 sales of them in 15 years, and I've sold two myself - (wish I had one of them back now)!
I don't deal much in modern coins so I can't say how that market is, but from what I do know some coins in PF70 are next to impossible to obtain (ie: 1995W
ASE PF70) others seem to be very abundant in the market. But the old adage holds here buy the coin NOT the holder!
"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013!
ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector.
See my want page:
http://goccf.com/t/140440