I bought a 21 ft travel trailer last November, and I pretty much travel by myself in a VW TDI Touareg as a tow vehicle. Not sure how long 33 gallons of fresh will last me, but I did think it worthwhile right from the get go to pick up a little used Honda EU2000i, which I pair with a Honda EU1000i that I already had, just in case I wanted to run the A/C when dry camping. Turn them both to Eco Mode turned off, and cool the place down, just fine with a Dometic 13,500.
I'd rather spend money on diesel getting 16 mpg towing and and a dump fee every now and then, than $30 + a night for full hookups every night. The travel trailer concept works for me, just a little bit of set up and tear down time leveling things out, lock the trailer up, and I'm back to getting 33 mpg while exploring in the SUV, or fishing, or a run into town for groceries and to dump trash, etc. 33 gallons of water can last 1 guy a long time with short showers.
It's all in how you budget and want to spend it on a trip, with or without FHU... anything I save on FHU is also the option to go out for dinner a bit while on vacation. That price tag of a night at a FHU for one person is pretty spendy per person, it's a better value if the whole family is staying with you at a FHU set up.