That is correct.

Unfortunately, the price of most everything is set by supply and demand. In the old days decades ago before modern, cost-effective cracking technology, it was more difficult to get more gasoline out of a barrel of oil. As a result, there was an ecess supply of diesel and other heavier components when the gasoline supply was met. But nowadays with the ability of refiners to get more gasoline out of a barrel of oil, and many refineries having set themselves up for increased gasoline vs. diesel, the tables have turned. With the cheap dollar and lots of diesel demand outside the U.S., the price of diesel has risen, since export markets are competing for it. And if the high price of gasoline causes people to drive less, it will exacerbate the problem since the major users of diesel have less flexibility in reducing their usage due to high cost, making the ratio of gasoline to diesel even more in favor of diesel.

And, as noted by others, the change in regulations in the past couple of years to reduce sulfur content has also increased the cost of diesel production.

I guess my point is simply that (A) I don't really see any conspiracy to stop diesels from becoming popular in the U.S., as the oil companies and auto companies can makes just as much, if not more, money selling diesels as gasoline, and (B) there's nothing unusual about diesel rising in price more than gasoline when demand allows the producers to charge more. As the ferilizer salesmen are saying to the farmers, if you don't want to buy it at this price we have plenty of people overseas that will.