a regulatory agency. Credit Card transactions in the EU, for example, are capped at a fraction of a per cent and they still make plenty of cash. Infrastructure providers are essentially just glorified landlords and should not be allowed to extract economic rents from market participants.
This is becoming a very blatant and obvious problem on a largely privatized internet. Enforcing low margin incentivises the correct behaviour which is openness and continued innovation. If steam would be forced to build new products rather than sitting on their platform we'd probably have had Half Life 3 a bunch of years ago.