its $2.50 per key, you have to actually buy them from the game itself not other people. To get the key, go in game click open crate and then if you don't have key, buy key, it will pull up dialog then you find the specific key you need, click buy which will pull up menu saying you need to buy credits or whatever the hell they call them, then buy 500, the lowest amount which will cover you opening 2 crates, you cant buy only 250 to open just one crate by the way, sadly....