Value of coins in a swap

Am I wrong in asking fair market value when swapping coins? Some people assume the prices in the swap list are the prices for the coins, banknotes etc. But I have found that they are usually WAY off on the value of most coins.  Some people get pissy but most understand.

I usually use e-bay sold listings for comps. 

ebay sold listing is usually the best way to determine a fair, current market value.

However, if the swap partner uses a different way to determine coin value, I'd apply the same strategy to my coins. That most often works out.

A seller (from ebay for example) always tries to make money, logically, so those prices always have a profit margin added, not counting the shipping costs that are usually very high (so that the price of the coin seems lower).

When I do a swap, I do not intend to get more benefit than exchanging coins for a similar value and making a balanced change, so I never use ebay prices but from catalogs such as Numista, Ucoin, Krause or even auctions. I also use, logically, the price that coin has cost me if I have bought it in my usual stores or suppliers (which I assure you are much cheaper than ebay).

The fair value is always the one accepted by the buyer

CREPOSUC

The fair value is always the one accepted by the buyer

That's it! Well said.

I usually buy my coins in bulk or at a local coin shop he sells the silver coins at silver price. So it is hard to price them from a purchase price. I use ebay because most of the other sites have wildly various prices and it seems the current sold prices seem to be fair. I have tried sites like Sammler.com for German coins and such. There are other sites for obscure coins.