Well here's some stuff (dually):
6 tires - over $900
Front and Rear Rotors - $400
one tire - $160
15qts of OIL and a filter - $55
Fuel Filter - less than $20
Glowplugs - don't even know but not cheap
Injectors (reman) - $100 a piece, i had to do one.
Tranny if you get that many miles - up to $5k
Fuel is $3 a gallon and only going to climb
CPS perhaps - never had to replace not sure.
TWO heavy amperage batteries - bout $90 with a discount
Alternator would be about $97
just to name a few, not all I've had to replace but some.
But on top of oil changes y'know you gotta do things like purge the water out of the fuel system or you'll have major damage, change fuel filter, high mileage change fluids like tranny, coolant, and diff fluids. And you'll probably have batteries, glowplugs, maybe a #8 injector, There's lots more than oil just because there are no dumb spark plugs/wires to change.
These things are expensive to maintain and drive. But TOTALLY worth it
But since you're an org member you have to take into account:
gauges - $300-400
Exhaust - mine came with the truck, but straightpiping cost $40
Intake - $269
Then you might end up wanting 500-600hp and you're looking at another $10grand if you're me.
All part of the game.