And if I paid you $ 9, I would not be charged $ 9, but $ 9 plus vat. And if Itch had a business presence in other countries, they would have to have localised shop system that would tell customers the vat adjusted price of things. Consumer laws are different around the world. As are tax laws and rates.
I guess you have to deal with irs separatly to tell them your income and deal with vat, if applicable.