I agree the price of fuel is important, I think Diesel normally runs about 30cents higher than 10% ethanol blend around here. I think if more people purchased diesels the price would fall.
The diesel folks have been telling me that since the engines are manufactured a lot better/heavier than gassers and designed to outlive a gas engine 2-3+ times, that maintenance cost is not really any different. They even said that oil changes aren't really that much higher and don't have to be done every 3,000 miles like gassers, so that balances out?
Resale value I've heard is way better on a diesel, which helps justify the extra cost.
I don't think the DEF (diesel exhaust fluid) costs that much, you can get it a NAPA and other places, as long as it is the correct ISO version. You can also add a gallon here and then if wanted. I think emmisions are improved by 60+ %.
Here is some info from the Florida Environmental Protection on the 70%water/urea DEF product.
http://www.dep.state.fl.us/air/emission/msc/vehicles/def_factsheet_07-16-09.pdf
