In an interview with Develop, Team Fortress 2 developer Robin Walker announced that Valve is now making the game free-to-play. The game will be supported by micro-transactions, meaning the only things that will cost money are items in the game's shop. If you can avoid buying goofy hats you can play this stellar mulitplayer first person shooter completely free. There is no set date for this price drop currently, but I will update when the information becomes available.
Source: Develop
Source: Develop