itch.io requires us to pay a minimum of $1 due to processing fees, which I didn't know until now.
Still picking it up, mind you, but perhaps keep it in mind for future sales.
You're right. There was no warning that I had noticed, but, I imagine it would be written somewhere on the site or the terms though.
I believe/think? the reason that the site permits it, is because the developer payout is still what is being advertised, while the itch.io fee is sort of a tax on top and is being displayed as its own separate warning before the player purchases the game.