The free only thing is temporary. Once they flip the switch to allow developers to charge, the developer will get 70% of the revenue and Google will keep the other 30% as a listing fee.

This is very similar to Apple's app store, where I believe the developer gets 70% as well, but the other 30% might be carved up slightly differently inside of Apple. As the developer, who cares, you're still getting 70% of whatever you charge.