All inclusive or in app purchases?

I haven't gotten to use Apple arcade yet, so I'm asking here, are games on Apple Arcade totally included with the membership or are there pay to play / pay to win / in app purchases? Are developers allowed to include advertisements?

I'm curious if this is just a way for Apple to make more money since they don't make very much money on free games that are app supported, but make much more money on pay to win or paid games.