Paid custom game modes, fuck off Valve.
http://blog.dota2.com/2016/03/supporting-custom-game-developers/
I mean we all knew this was coming. That was the entire point of custom games.
The most unfortunate thing here is that hat creation is now no longer the (potentially) lucrative semi-volunteer work it once was because the pipeline, the standards, and secondary market were all mismanaged to hell, and I see the same happening for custom games one day down the road if this ever takes off.