By higher maintenance costs I'm guessing he means you need to change the fuel filter every 20K, that's about the only difference between the EcoD and the gasser...I won't even mention changing spark plugs since that's a 100K miles occurrence.
If you want to say oil change (premium full synthetic oil change) I can change mine for shade over $60 including filter. It actually cost more if you eun a premium full synthetic (Amsoil, Redline, PUP, Mobil 1, etc) and change the oil every 5K on a gasser which is appears to be a popular oil change routine on this forum.
The Gen3 EcoD hold 8.5 quarts to the Hemi 7 and is 10K or the Oil Life Monitor (whichever comes first).
I'm surprised the "massive" DEF cost wasn't mentioned, it about $0.001 per mile(no, I didn't stutter with the extra 0).