The one time model from Apple/Android really is just a tax that gets you nothing but access in comparison. It's a full advert model where the biggest players throw millions at Apple/Android for visibility.
Valve's somewhere in the middle of the two. No "p2w" adverts but it's not doing too much to draw devs (except reducing the tax for AAA devs). It doesn't need to. A lot of its community models are "we're having a party, you bring the food and drinks".