Many people can save fuel money driving something other than the TV as a DD. A 5 year old used sub compact that gets 35mpg and has little depreciation over 2 years/20k miles for example. But then you are driving a 5 year old subcompact, or brand brand new Cruze vs. what is presumably a much nicer and comfortable vehicle that is used for towing.
My wife drives our TV to work, about 35 miles per day. It replaced a minivan as family hauler and at 14mpg vs. 17mpg isn't too bad a hit on fuel esp compared to the vehicle cost. However, I drive at least 50 miles per day commuting plus extra trips, lunch, errands, etc. I absolutely love my Passat TDI. My lifetime average is 38mpg over 38k miles and could easily be higher but I just enjoy the torque too much to care saving $20/mo. It drives like nothing else that gets 30mpg (except maybe a Tesla Model S) so I don't feel stuck in a penalty box. Since I'm tall, the large cabin is important.