Ditto on that. The main extra cost that I've seen is the larger volume of oil required for a diesel when you change the oil. Filters are also a bit more expensive. But this is hardly a major cost. I'm spending under $100 for synthetic oil and the fuel filters runs about $60. Oil filters are the same as a gasser. Other than that there have been no extra costs. I did change the air filter but that was 10 or 15 bucks. I have 84K on the truck.
That truck pulls my 34ft 5ver up the mountains out west like they aren't there. One word of advice, get a one ton not a 3/4 ton. When you look at the price difference vs the total price of one of these trucks the difference is tiny. The people who say: you don't want too much truck are just people who bought a 3/4 ton and are trying to justify their purchase to themselves. The trucks look the same, handle the same and burn the same amount of fuel. Why be limited by a 3/4 in the future if you want a bigger trailer? Remember that diesel will last a long long time if you treat it well.