I thot tf2 was free... am i wrong??....
Keys unlock boxes. Boxes have in-game items. Valve's very clever in making money off TF2 by allowing users to sell keys, boxes, some rare items found outside boxes, and many items found inside boxes using their own p2p marketplace (they charge very high fees - ~10-100%). Almost all items which can not be sold via their own p2p marketplace can still be traded, but Valve does not permit these to be sold for money since they sell them themselves at outrageous prices (where an item would be worth $.01 if allowed to be sold in the p2p marketplace, Valve disallows this on some items and instead charges something like $9.99 for it).
Virtually everything in the game which isn't a special event item can be traded or marketed (the "marketable" tag means it can be sold on Valve's p2p marketplace) EXCEPT keys, which exclusively come from buying from Valve or another user. True f2p users would instead use the game's crafting mechanics to create refined metal from drops they get just from playing ~10 hours per week. I think it's something like 4 refineds for a key. Valve combats these "freeloaders" by having key purchases from Valve directly permanently upgrade a user's account to "Premium," which allows for more rare timed drops among other benefits, which makes "aftermarket keys" slightly less valuable. Any purchase of TF2 items from Valve gives Premium status, but keys are really the only reasonable purchase to make (though a key purchase from Valve directly costs $2.49, a standard box's contents are usually worth ~$1.50, while uncommon boxes can be ev-neutral or even ev+). That said, a f2p user can still become premium by selling marketable items in the p2p marketplace for a Steam wallet balance, then use that to purchase a key directly from Valve, and that's the really cool part about Valve's policies here -- you can still have anything you want without paying so long as you value your time at ~$.05/hour.
