We've done long and short trips and I keep a pretty detailed log with our costs. Not that we really make any decisions based on the travel cost, more just out of curiosity. We go where we want, when we want and do and see things along the way we like.
My cost/day covers about 300 days over the last 4 years. We do eat out occasionally. When we are in a small town and see/hear of a good local eating establishment we will patronize it. Lunch is our favorite. Have found many a small town with some outstanding eating establishments and it's fun to talk to the locals and learn about the area, find things to visit etc. Otherwise we fix and eat in the trailer.
And we often will pay to go through museums etc. Starting last year DW hit 62 so we no longer pay for National park, COE etc visits and often get the 50% discount on camping fees.
And about 1/3 the time we have grankids and DD, SIL with us which we included in the costs, rather than separate them out. That's part of the fun camping, letting the grandkids see the country. My cost/day includes groceries and eating out. Not clear if yours included groceries
Our average is a shade over $80/day. So at $55 your doing very well. BTW I have a good friend that did several cross country trips and we were comparing costs one day. His was also a shade over $80/day.
But like someone said, we spend more than $80/day sitting at home!! And there is no way we/you could do this kind of trip using hotels for anything close to this cost/day.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!