I had my 06 with the 5.9 Cummins / 6 speed for 200,000 miles. Replaced front pads at 100K and the rear pads at 175K. I did put a new clutch in the truck at 150K since it would slip pulling my 40 ft Toyhauler when I really jumped into it, but other than that, a couple UV joints and that is about it. Front end was perfect and drove tight the day I traded it for my current 14 3500 Cummins. The 14 has 102K miles on it now and it's been flawless. I don't "like" the extra emissions stuff, but so far, they have had no real affect on me or what I use my truck to do.
I don't see regular maintenance as real expensive. It isn't cheap, but I change the oil/fuel filters every 15K miles and the air filter about every 30K. Again, it isn't cheap, but it certainly isn't 1000's of dollars a year. I loved the 06 Ram, it was a bullet proof rig that hauled my 40 ft RV all over the country, hunted Idaho, Wyoming and Oregon yearly with not a single problem. The 14 has been excellent and hope it is reliable as the 06 was. It is another manual tranny and just gets it done for me. Also, my front end is still tight as it was with 5 miles on it and wears tires evenly (third set coming up).
I could get by with a gasser until I hook up to my toy hauler, then, that is when the diesel is at its best. The new ones wanna work or at least run on the freeway. If you are just piddling around town, I think the DPF and other pieces would have to clean itself regularly. If you have the ability to run the truck and will work it, you'll love it.
