My dual sport Yamaha 4 stroke gets 70mpg and needs very little in the way of servicing. I think it would be anti mustachian to sell it as I use it for trips to the store, running errands, and having fun on mountain trails.
I did the math on my Katana 600 and it pays for itself if I do somewhere between 600-1000 minimum (low/high based on the range of typical gas prices and maint/repairs) miles a year on it instead of the car. I'm not there yet, but next year I may be.
I'd really like to see those calculations. Every time I've had this discussion with people, and it's fairly often, it's not even possible to break even. It may get closer to possible if you are talking about trading miles in a 10mpg gas hog to a 75mpg motorcycle but that's not the reality for most people. Also any motorcycle owner will rack up pleasure miles that they wouldn't otherwise. Those miles will kill any potential savings.
1000 miles at 75mpg = 13.34 gallons of gas
1000 miles at 30mpg = 33.34 gallons of gas
Difference of 20 gallons @ 3.50 per gallon = $70
So your total operating costs including registration, insurance, repairs, maintenance, depreciation and opportunity costs for the value of the motorcycle is < $70 per year?
I guess you could argue you are negligibly negating some portion of the depreciation of the car but 1000 mile per year will make almost no difference.
Did you mean 6,000 - 10,000? That would put total costs at < $700. Closer to possible I suppose but I don't know many people that can rack up 10,000 commuting miles on a bike.