Any diesel will be expensive to repair, be it in a pickup or a MH.
With that said, the last time we spent a lot of $$$ on repairs was went we owned our 1990 Fleetwood Flair.
Since then we've owned a 2000 Newmar Dutchstar gasser, a 2003 Newmar Kountry Star DP, and a 2008 Newmar Kountry Star DP. Other than normal maintenance (oil and filters) - and I hate to even say this as I'll jinx ourselves, we have spent exactly $0.00 on any kind of chassis repair, and close to that number on house repairs. The 2 big ones on the house were a cooling unit in the refrigerator and we currently need a new AC. Obviously neither of those are DP specific and could happen to any make, model, or type of RV at any time.