The maths

At a ten percent platform fee that's $2,400 gone in a year. A flat plan costs the same whether you sell $200 or $20,000 — which is the whole argument, written as a number.
The better the year, the more it takes. That's how percentages work.
The plan price doesn't move when your revenue does.
Stripe's processing fee applies either way — that part is honest on both sides.

0% platform fee on Starter and Pro; Free Plus keeps 30% of each sale. Stripe's processing fees are its own.