Yeah, if I was towing a lot, almost daily, and for long periods, I could justify the diesel. I did some general figuring on this....
On average from various forums, I have read that the Dmax version of any 2500/3500 platform is about a $8K premium in price. Now factor that over a 100,000 miles, and you have roughly an 8 cent per mile cost of operation spread just in equipment.
Now factor general mpg numbers and cost per mile. Seems like a lot of the 2500 crowd is getting roughly 12 mpg averages on the 6.0L (I get around 14 mpg average for all miles, but we will stick with the 12 for this discussion). That would equate, at the current $2.10 price for regular in my area, about 17.5 cents a mile in fuel cost. Now just to break even on the purchase and fuel consumption, the cost per mile just for fuel on the diesel would have to be 9.5 cents a mile to bring the cost of purchase and operation between the two engines in balance. At the current average cost in my area for diesel, $2.80, the diesel pickup would have to be AVERAGING 29+ mpg just to break even from the additional cost of the diesel option in the pickup! That is not going to happen.
And we didn't even factor in the higher maintenance costs of the diesel platform over the gas, which is going to be when you consider the larger oil sump capacities, more filters, DEF for the SCR unit (when it works right), and cleaning of the DPF filter, or an out right replacement (OUCH!).
Except for the serious, dedicated hauler, the diesel makes absolutely no economic sense. It is a viable option in the right circumstances, but for the average user, getting a diesel only makes a statement, not a sound decision. That is why I chose a 6.0L in my new 2500HD, same as a vast majority of the business users of 3/4 and 1 ton pickups in my area, including the farmer's coop guys who regularly haul feed, tow anhydrous ammonia trailers to farmers, etc. Most of them are now on 6.0L gas instead of diesel.
