The grandkid aspect is important. Last year we made three trips to northern Virginia (Washington DC) on account of daughter and granddaughter. Two of the trips were by B and one by flying. The two trips by B were cheaper than the one by flying.
This year we combined our first Virginia trip with the RV.net B rally that got us half way there and the Indy 500 race on the return. All in all, so far this year we have put on 4,500 miles, spent about $800 in fuel, maybe $200 in camping fees. But we have been to see our granddaughter, two B rallies, my annual high school reunion and a major auto race, and, ahem, 11 pork tenderloin sandwich opportunities in 5 states.
We've camped in 6 different states. I figure during that time away from home we probably would have expended $200 worth in gas for local travel. Food and other necessities are probably a wash. So the whole experience over 3-1/2 weeks out was maybe a net $800. That's cheap for what we got. We can no longer fly to Washington DC for that.