If you consider the per seat cost compared to commercial, I don’t think making it a bit more expensive will move the needle.
Maybe there will be a point where it works out cheaper to fly to another country to fuel up though. I'm sure some tax policy folks could figure this out better than I.
Tax the ~~rich~~ ultra-wealthy, and their thoughtless damage to our environment. It's about as close to a victimless tax-rise as could ever exist.