When I made my budget in 1990, I figured I'd spend around $10k/yr (about double in today's money), but I spent <$3k/yr.
I actually was enthralled by nature... wandering around the "neighborhood" to see what the critters were up to. Sitting awhile, walking awhile. No phone, internet, or even computer in those days, and hardly anyone camping on public land. No solar, no refrigerator or cooler, no heat; simple. Driving to town once a week for supplies doesn't take a lot of gas.
Anyway, it can be done cheap or expensive. Doing lots of driving is expensive (usually >50 cents per mile if you are realistic), and so is having all the "stuff" that you are accustomed to... which needs to be maintained/repaired/replaced on a regular basis.