Where's the pricing information. I hate it when a site hides it's pricing. My immediate reaction is that it's too high. Then contact with the company to find out is going to be fraught with listening to justification before I can get prices and immediately rule them out as too high a percentage of expected revenue.
This comment is a bit off topic as the post isn't about Clay.io, rather games in general.
However, to answer your question, we take a 20% cut on any transactions made through selling games or our in-game payments API. If you're using our Advertising API we take 10-30% (depending on where the game is being played). Everything else (leaderboards, achievements, etc...) is free to use. This info is displayed here: http://clay.io/docs
