Uh, no, the 30% sales tax is NOT the same as VAT. It's something Itch has to pay for you because you're technically selling out of the US where the site is based. VAT is applied on top of the base price, and yes, Itch also takes care of it for you if you choose that option.
You only have to worry about the money Itch sends to you; ask a local accountant to be sure, because it depends on your country's laws.