Generally the diesel MH are diesel pushers vs front end gasses. Just looking at the engine "maintenance" it's pretty much the same - oil changes. Yes it cost more, probably double. But if it's a couple hundred dollars that your afraid of, your missing out on a whole different set of benefits. Air suspension, air brakes, no spark plugs, better gas mileage, longer engine life,quiet,and more. Honestly I have my oil serviced every year for about $300.00. Air filter every two years. Coolant checked every year. So after 3 years it's cost me about $1000.00. The benefits far exceed the negative.
Not sure why everyone thinks "engine maintenance" cost so much more. It's not that much. The other systems that go along with owning a diesel pusher add some additional costs. But you mostly won't find these features in a gasser either.