Well I guess if you look at those parts in terms of hot rod parts I'd say they are in line. 7.3 is yesterdays' diesel. Look at a 6.0 sometime.
Here is my cost per mile including fuel for my 99 Dodge CTD for 175,000 miles. I do my own maintenance and repair work both car and diesel.
.29 per mile includes fuel at todays prices... Dodge diesel truck 175,000 miles still running strong. better than 1/2 for fuel
.37 per mile includes fuel at todays prices ...98 Windstar Van. Dead in driveway ready for salvage. Better than 1/2 for repairs.
These include purchase prices too.
I'll be the first to admit that diesels are expensive to fix but if you only fix them once in a great while, the cost per mile is not so great. I fully expect to get 500k out of mine whether towing or cruising. The longer you drive it the better it gets.