Well, actually, the average person will probably not save money, overall, by riding a motorcycle as opposed to driving the average sedan. Yes, fuel cost is less, but maintenance tends to be more frequent and more expensive, as well being harder to schedule and get done on an immediate basis. Add to that the cost of tires that last less than 10,000 miles and cost much more than auto tires, and it is a very lopsided proposition.
I rode a beater VT500 as my prime transportation for two years, and I was able to save a lot, but only because the bike was cheap (free), I did all my own work, including mounting and balancing tires, and the bike was, after all, a Honda, and there were no major mechanical problems in that time. The average commuter is not going to put up with all that to justify a 50% gain in fuel mileage.
Compare the maintenance structure for automobiles vs. bikes in this country. What is the motorcycling equivalent of JiffyLube?