Epic has asserted and proven that you don't need to take 30% to run an app store and approval pipeline. The incredible amount of profit generated by the iOS store is further evidence that the cut doesn't need to be 30%, as is Apple's sudden willingness to make exceptions for big companies like Amazon and temporarily offer 15% to small companies.

Neither the Epic Store or Steam on PC are built around selling your data. Epic's PC store charges 12% (and if you use Unreal, they waive the licensing fee for that engine too), and Steam has a special tiered tax for massive companies (something like 25% for 50m+ in revenue, 20% at some higher tier)