We did a 2.5 month long trip last fall and spent just under $6,000. We didn't really eat out but once or twice, we boondocked mostly, and we didn't use it as a basecamp. We would pick a route with things we wanted to see and do them...when we were done for the day, we found a place to park it to overnight or researched a head of time.
NY to Colorado (stopped for one night), Utah to nv, to AZ, NM and home. The most we stayed in one place was maybe 4 nights except for visit to son's Las Vegas parking pad (in and out a few times for long weekends as they work).
I think that is pretty frugal given what we did. We are not sit on your bum kind of people.