As others have said, you have to refine the oil which costs money.

Petroleum (crude oil) is a mixture of hydrocarbons, basically chains of carbon atoms with hydrogen attached. The molecules come in different lengths, the shortest (with one carbon atom) is natural gas, then you get into your heavier gases (butane, propane, etc) and then liquids. Liquid fuels are actually mixtures of various chain lengths, the weight of the fuel is determined by the average carbon chain length. Diesel/Jet A/Kerosene are amongst the lightest of the liquid fuels, then gasoline, then heating oils.

As things get even heavier you get into lubricating oils, then grease, then tar (used for roofs and to make asphalt).

The refining (cracking processes) basically uses hot steam to boil off the shorter (lighter weight, more volatile) molecules from the base petroleum. As the stuff moves up the column, you pick off the weight of molecule that you desire. The heavier stuff stays lower...tar is at the bottom IIRC.

Once refined, the demand vs. refining output can cause price disparities between different products. Gasoline costs more at the pump than jet fuel, but you also have to account for the fact that it may have extra additives (ex. techron) and is sold in lower volume.

Because liquid fuels are a mixture of chain lengths, there is not a set amount of a particular fuel type in a barrel of crude. Since gasoline and jet A share a lot of the same length molecules, you can weight the process to produce more gasoline at the expense of Jet A or vice versa. If this is misaligned with demand you can get weird price disparities.

You could also weight the process to make more heating oil in the winter which might somewhat cut supplies of other products.