Cost per gallon of fuel is not the reason I went for a turbo diesel. I went for the increased power delivery that comes from the turbo vs normally aspirated gasoline. Having driven heavy vehicles with both types of engines, a turbo diesel will out pull a gas engine every time. A boosted engine is much more efficient than a NA engine under loads and cruising. Gasoline boosted engines have the same abilities but require priemum gas. I have driven turbo'd cars for years, but when it comes to moving heavy loads, turbo diesel is the best way.
It's not really comparing apples to,apples, the engines are so different and most people are not familiar with turbo diesels. Look at the trucks used to pull heavy loads, 18 wheelers, construction trucks, farm trucks, etc. They are turbo diesels, period. Why? Mountains of torque with no,worries about pinging (pre-detonation) that will destroy a gas engine. It takes a huge gas engine to equal a turbo diesel's torque.