My good fellow, attending Yosemite, aside for the very small minority of nutcases like us on this forum, is pretty much the textbook definition of an elastic good. There are so many reasonably similar alternatives that are cheaper and closer to populated areas that there's no way a marginal increase of $30 (^ +75%) isn't going to result in a huge decrease in attendance.
That's especially true for low- and middle-income families,
who have largely seen no real wage growth since 1973. That thirty bucks is groceries for a week, or a big chunk of an electric bill. It's important, because when you're living on the edge, every dollar matters.
The real scandal is that we haven't chosen to fund the NPS to such an extent as to make attendance free for all citizens. America's National Parks are our common treasures and should be treated as such. We should be encouraging more people to go explore them, not erect even more obstacles to prevent the marginalized masses from visiting.