Players get listed on the market for a price higher than their market value (the one you see on the cards).

While players are on the transfer list they drop in price for each minute there goes until someone buys the player or the deadline of the auction is reached.

Typically the end price for all players is the same as the value on their cards (younger players might end a bit above that as they are very easy to train and improve in value).

So, don't overpay by buying a player too early, but don't wait too long to buy as some other manager might find the price attractive as buy the player before you.