According to information coming out of Valve's Steam Dev Days event from Steamdb, Team Fortress 2 and Dota 2 content creators were paid a collective $400,000 in the first week of 2014.
"In the first week of 2014, $400k was paid out to content creators", noted Valve during the second Steam Day. The content in question is made by ordinary players in the community who then resell it to fellow players.
Valve said that more than 90 percent of the content in Team Fortress 2 is created by the community. Valve also revealed that more than one million Team Fortress 2 player accounts have sent gifts to other players, and nearly two million have received them. Around 17 million accounts own items created by other people, and a pool of 500 million items it out in the wilds of the ecosystem created by Valve.
For more interesting statistics about Valve's popular games and micro-transactions, check out Steamdb's summary of the event here.