they didn't have tf2 sales or tf2 mann.co stores 3 years ago nimwityou got to play a couple years before all the f2pers, it's kind of like buying a game that's $60.00 when it comes out and then they lower it a month later to like $40.00 and you demand a refund.
There have been several occasions when the game went on sale for huge discounts.
It was ultimately Valve's decision to do so.
It's like me getting upset at Infinity Ward/Activision for dropping the price of MW2 to $30 when I bought it for a full $60 even 6 months after its release.
It's not something you're supposed to be butthurt about.