Where'd this $5000/car(/yr?) number come from? Total cost of ownership for a car is far less than that. You can only really get to $5k/year through very high depreciation, and people buying those kinds of cars won't be riding your busses anyway.

Also, $100/hr to run a bus is probably a fine operating cost number, but you do have to buy the bus (capitalized cost) and take the depreciation hit just like cars.