First, I seriously doubt you got 2.2mpg better towing because of non-ethonal fuel.
Ethonal has roughly 80% of the BTU content of gasoline. So a 10% blend should only result in a 2% reduction in MPG. Unless you typically get 100+ mpg towing, it wasn't likely because of the different fuel.
When you jump states, the cost differences are mostly about the state fuel taxes but ethonal is a bit more expensive to produce.
They did it originally to reduce emissions. Then it became a political game related to supporting corn prices...I'll leave you to dig around on the internet and sort out fact from tin foil hats once it gets into the political aspects.