This all really depends from developer to developer. Usually they have a patreon page and you can see how much they are bringing in a month. I know if I was making a game I would not be making all my expenses public.
This really heavily depends on the skill of the developer. Aside from programming, do they do the animations and create the models and stories themselves? or do they pay someone to write them and do the animations? these things make a big difference in how much the game owner will profit.