The dumbest thing, I've ever heard from FOSS folks: "Why don't you use open source licenses for your stuff. You can ask for a price there too!"
Yeah, but nobody wants to pay it, when the license, literally, requires me to share it for free.
It's the same with pico-8 games.
Technically you can sell them. Practically, very few people will buy your game, if any.
So, yes, you can sell your pico-8 and FOSS games.
But you don't want to do so.
Those games who have any success with this model, btw?
Those who left the FOSS and pico-8 bubbles and got customers from outside.
Why
The answer is pretty simple. In those communities, asking for compensation of your work (aka. asking for a price) is seen as unethical.
And yes, that's a hyperbole, but it's really not far off the truth.
It's seen as tone deaf, when those communities are 100% about sharing things for free.
So my suggestion: Use a proprietary license
Just saying for itch, the cut can be between 0% and 100% of every transaction and YOU choose which.
SO you can keep everything for yourself (though, I'd suggest to share 10%, which is a third of most other platforms)
Anyway, how to be successful?
It depends! You need a community or else nothing will go.
What do I mean by "community"? Well not the regular stuff of mutual aid, but more you need fans. You need people excited about your game!
How do you get people excited? Well, lots of things. Sharing art of it and having it about kinks worked well for me. But it heavily depends about what you want to do.
But let people know what you're doing. Otherwise they won't get excited about your work.
I'm telling you these things, coming from a FOSS background and making pico-8 games.
I have experience with both and making "regular" games. And the community, you are posting into, matters the most.
Pico-8 and FOSS are not good ones. Heck, even itch.io I'd say is not the best (but the best we've got)
Steam might be better, because people are more used to paying for things, but the massive $100 hurdle and 30% cut is very discouraging.
Btw. itch takes 10% by default and you say what it gets.