Most of the costs he mentions (registration, insurance, and some part of depreciation) are fixed whether you drive the car or not. I think that might also include finance charges, which you may not have.

The actual operation costs are more like $0.15/mile. They usually figure maintenance is about %50 of gas costs. Obviously this is much less if you maintain the car yourself, and much more if you insist on having your Hummer serviced at the dealership.