Close
You look at the sale price and make an educated decision. You need to remember you make the price not anyone else. Just because someone is looking for game "x" for 4 TF2 keys, doesn't mean yours is only worth that much. But it is also a matter of finding what someone is willing to pay, and usually what people will pay is close or slightly above the last sale price of the game.
Is it by cheapest price when it's on sale? or by it's worth in the Russian Steam Store?