In 2014 we did 10,000 miles in four months through the western U.S., Vancouver to Ottawa (down and around the Great Lakes) and then returned through the mid-west, down through Texas and back home to northern Mexico.
During that year, fuel prices were sky high to the point we paid up to $1.37 a liter (Canadian) and didn't find low prices until Arkansas at $2.14.
We boondocked in Lowe's, forest service, Home Depot, friends, state parks, and took advantage of PassPort America, Taco, GS and used GasBuddy as our fuel guide. We ate out on occasion but never denied ourselves any pleasure.
No way did we even come close to spending that much, in fact, we finished at about $5500.