You can use the 'Transfer Compare' button in order to see what a similar player has recently been sold for on the market.
There is some debate over the usefulness of Transfer Compare, as some people feel is does not price players with any great accuracy. The main accusation is that it does not accurately account for the value of secondary skills.
Winger comparisons are particularly badly served, as wing, playmaking, stamina, passing and defence skill are all used by transfer compare to set a price.
There are other ways to check for current transfer prices: Transfer Price Evaluation