It's 5 USD. Even in my country where our money isn't as valuable It's generally pretty easy to afford. Only hard part is when/if your merchant card has Itch blocked. I had to buy a gift card to bypass my merchant card's security settings.
The reason why the other versions don't require it has already been explained to you. Furthermore, the creator is already considering putting the others behind a price tag already as they stated prior in a separate thread. The only reason someone would have an issue with the 5 USD is due to their status as a minor.