It’s worth mentioning that users that bought your project when it was set as “Set a higher price for this file” do not own the game, so they won’t have access to new files uploaded to the project. This is at least my understanding of how this option is meant to work.
I think it would be better to find a way to give access to the project to those users, but that’s something I’m not familiar on how to do, and it’s also your call if you want to do it or not.
I feel like I need to point out I’m not part of Itch in any way, I’m just hosting my projects here. I just like helping people when I can :)