I think you're misunderstanding me, but I'm not sure how to articulate what I mean. I'm gonna try though.
Take this as an example: https://fouzi94.itch.io/existence
Notice how it doesn't specify the price up front, but if you scroll to downloads it has files listed for "If you pay $*** or more"
I just wondered if there was a way to specify the full game as "If you pay $25 or more" in the individual files.
For some reason itch sees this differently than the full game price.
I know cause other games were like "if you pay $3 or more" for certain files, then later an update was uploaded as "$5 or more" and I only had to pay an additional $2 for the new files.
If that's confusing, I'm sorry. Honestly idc if I, personally, have the walkthrough or not, I just wanted to try to help you out.