In the US diesel taxes are often different from gasoline, but polluting is generally not a factor.

Jet fuel and diesel fuel come from similar parts of the barrel. Refineries can largely choose what kind of fuel they produce for a given unit of input. One barrel doesn't always split into the same fractions. There is configuration involved.

This started, I believe when fracking became a major thing (the late 2000s), because shale oils tends to have less heavy hydrocarbons then the old wells.

And the ethanol makes the fuel less valuable (energy reduction per litre) moreso than biodiesel.

I was always under the impression that a big part of the difference in cost is largely due to taxes.

While diesel is less refined, the difference isn't much. These days both are heavily refined products, and the cost to refine gasoline isn't very much per gallon.

The real answer: supply/demand is the key factor in the price you pay. Cost to create/build a product generally sets a floor on the price you pay: a business that isn't making money will stop making the product (loss leaders exist, but not a factor here).

Rule of Acquisition number 35: Peace is good for business.

The main caveat is that available models are heavily weighted towards “compact” (RAV4 sized) SUVs and larger. There aren’t many little Prius/Fit/Soul type town car models around which is a bit paradoxical with that being the use case that EVs have been well suited to for the longest time.

I think cost per kilometre/lightyear/rod is close