It depend, the more you are successful on Patreon, the lower will be the part comming from Steam; will, obviously, still being the majority of your earning.
A not successful creator who would earn US$ 100/month on Patreon can easily sell more than 10 games at US$ 10 each month on Steam; at least on average at the end of the year. It suffice that 600 persons cross his game and think that, for this price it worse it, for him to have 80% of his income that come from Steam.
Strictly speaking, one can assume that the same apply for a creator that would earn US$ 1000/month. 6,000 Steam users buying his game don't seem impossible from a platform with 132 millions active members each month. But there's a mechanical limit due to the fact that Patreon and Steam don't attract the same population.
Patreon users, at least when it come to adult games, are recurrent players who want a big part of their games to have lewd. This while Steam users are more casual when it come to adult games. Even if they are hardcore players, globally adult games are just a distraction for them, something they'll play once in a while to change their mind.
There's obviously an intersection between the two populations, but it's something marginal.
And it's where the limit apply. The higher will be your earning on Patreon, the harder it will be to find enough persons to buy your game on Steam in order for those earning to be a large majority of your income. The highest know Patreon income for an adult game creator is
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with US$ 88,524/month. I don't know if his game is on Steam or not, but it would need around 44,000 persons who buy it still at US$ 10) each year to reach the 80% earing comming from Steam. Something that is more difficult to reach when you mostly face pure casual adult games players.
It's not impossible, there's some really sucessful adult games on Steam, but proportionally it's even more exceptional than being successful on Patreon.
What, obviously, doesn't mean that Steam doesn't, or wouldn't for those who don't have their game there, represent a big part of the earning even for Patreon successful creators. It's just that, proportionally, the more you earn on Patreon, the lower will be the Steam part in your global income.