iminhell, I totally get what you're saying, but since I own a TDI Jetta, I figured I'd shed some light on your numbers. (given this is just the jetta, I have no experience w/ any other diesel vehicles)
First, since we've had the car, we've been averaging 49-50mpg (80% highway)
Second, you've got the part about the filters a bit wrong. The oil filters for the TDI are ~6 bucks, and oil can be had for ~6/qt AND VW suggest you change it every 10k miles (being synthetic) so we'll call that even w/ a standard petrol engine w/ synthetic oil. The fuel/water filter on the other hand only needs to be replaced every 20k miles (for ~35/20 bucks that you mentioned)
So 75% of 20 bucks, we come to $15 more per year on the Jetta than I do on my SVT, all while getting about 25mpg better. After looking through the Jetta TDI maintenance schedule, and talking to a dealer, the fuel/water filter is the ONLY additional expense when compared to a standard car.
Sure, what's ~750 dollars less spent on fuel per year except maybe 2 car payments?