From another comment you're good as long as the price is never raised above $10. Itch's per-file pricing makes no sense that you can over-pay and be fine, but if you "under-pay" because of a price change you can't make up the difference. Enough people need to raise Hell to Itch, until they change their stance. They'd rather blame game devs for using it "wrong".
I created a feature request #1775 on the itchio Github. Maybe if enough people pile onto it it will get addressed.