The fact that the fee is the same for Steam and Apple/Play Store seems suggestive to me the market is warped, given the latter ones are cases which are clearly monopolies where no alternative is technically possible.

Steam has a "most favored nation" clause which means people can't charge less on Steam than they do on Epic Store. And Epic Game Store cut is 0% on the first million and only 12% after that, but it can't actually end up charging less to customers if Steam maintains the most favored nation clause.