Cowboy - - - Even though the cost to make diesel fuel, is roughly 1/2 of the cost to make gasoline - - it was only 1/3 before ULSD, the high cost is due to four things:
1. Diesel Fuel users are unable to use any thing else that is reasonably priced.
2. The federal government (EPA and Calif) decided diesel wasn't "clean enough" and mandated unreasonable regulations be met in an effort to "Clean up the Universe"
3. The oil companies, thinking diesel fuel was the future fuel for the USA, as is in the rest of the world, started pushing up the price to keep the fuela cost per mile at the same rate as a gasoline powered vehicles,and so buyers wouldn't get "sticker shock" when the price started to go up. Since Diesel fuel wasn't universely accepted, and the prices were already up, and buyers were buying, there was no incentitive to lower the prices.
And Finally - - -
4. "Because they Can"
Denny