Then, when they are done, you get to skim big chunks of their revenue with app store, payment processing, etc. Don't forget to sell additional advertisements, to other game devs, on top of the places where you list their games!

All of the profit streams above scale with the number of devs and the total size of their market - not with the success of the average/median dev.

It's the same thing with other professions where people provide their own sense of mission and self-fulfillment: teachers, home health aides, VFX artists in hollywood... These are important, in-demand professions, yet they get paid poorly because their drive and passion is counted against their compensation.