I don't think I've ever heard anyone say that diesels are not more expensive. That's a new one on me.
To the OP. If you do a search, you'll find hundreds of posts on this very subject.
To answer your two statements...yes, diesels are more costly to maintain. Keep in mind, even the smaller diesels require at least 18 quarts of oil, large oil filter and in most cases two fuel filter. In addition, a very large air (and costly) air filter, hydraulic filter, water filter, and a host of other required maintenance items.
Even if you do you own maintenance, the cost of the oil/filters will be far more than a gas rig.
And....if it is maintained correctly, more than likely the diesel "engine/trans" will out last a gas engine/trans.
There are a host of other pro/cons that you need to consider and your best bet would be to do a search like I first mentioned.
Good luck in your quest.
Ron
Ron & Sandie
2013 Tiffin Phaeton 42LH Cummins ISL 400hp
Toad: 2011 GMC Terrain SLT2
Tow Bar: Sterling AT
Toad Brakes: Unified by U.S. Gear
TPMS: Pressure Pro
Member of: GS, FMCA, Allegro
RETIRED!! How sweet it is....