VW's common-rail TDI's that frag high-pressure fuel pumps to the tune of $10,000 and have all sorts of techno-wizardry in the exhaust and all the diesel pickups that have either DPF systems or urea injection plus all the fancy variable-vane turbo stuff. All that stuff costs money up front, and money down the road to fix later when it breaks.
A VW Jetta TDI doesn't get better fuel economy than my gas-powered Cruze (okay, 2 mpg better city at 30, same 42 mpg highway), costs $4-5k more to buy, still has problems with the HPFP, and the fuel is $4.19 a gallon instead of $3.75. Add in the DPF in the exhaust that costs far more than a comparable catalytic converter along with typical VW reliability, and it's a recipe for an expensive to own car. Fun to drive, yeah, and still expensive.
If somebody wants a diesel pickup because they tow 10k lb trailers 4-5 days a week for 50+ miles at a stretch, they're going to save fuel money over a comparable gas pickup. For Joe Commuter who hauls air, the gasser is by far the better choice for total cost of ownership, and future maintenance down the road.