i really dont see where maintenance is more expensive. a diesel ‘tune up’ consists of a fuel filter and a bottle of fuel additive, which will run you like $20 tops. what gas engine can you tune up for less that $20?
you cant even think about turbos and injection pumps as regular maintenance. i had a 95 chev with a 6.5, which is argued the worst diesel made(i know), it had 200k miles with no maintenance done but fuel filters and oil changes. original injectors original injection pump, original turbo, etc. thats like thinking cylinder heads on a gas engine are regular maintnence consumables.