Theoretically products could have different refining costs, based on time at a given temperature and pressure, or some similar algorithm, but it is also true that a global cost could simply be calculated for all products by for example just taking a year's of the refinery's capital cost + a year's of its operating cost and dividing that total cost by the total number of barrels processed during the year. That would give you the same refining cost per barrel for each product run through the refinery. The problem with that method is, while it may be convenient to consider it so, it is also obvious that a higher market price product would be able to adsorb more of the refinery processing cost than a cheaper product simply by applying a same percentage markup.
You also have to remember that volume purchased at any one sitting can impart large differences into the cost factor involved too. That isn't going to make sense when taken into the above refining cost algorithm either. It obvioulsly isn't going to make much of a difference in cost in producing 1 bbl of gasoline, or 1000 bbls of gasoline in a continuous process, but transport and storage have some factors that might result in differences that would affect the per bbl cost of transporting 1 bbl or 1000000 bbls.
There is a theoretical relationship between all hydrocarbons based on simply the equivalent calories each one brings to the table, there are many other variables that can affect that simple comparison. While they all have theoretically interchangable calories, each form of fuel is not exactly and totally interchangable with another when it comes to determining one value in a particular form and at its particular point of use, but those finalities must be worked out by middle men of the cost of the supply chain. So despite all the above, if your company is the ony one that can get a useable fuel to a consumer at the top of some remote mountain top, you're probably going to be able to ask for a premium for doing it too.
You could obviously make as large and as complicated an algorithm to determine cost based on logic as you have numbers to enter into it, but then you still must consider how much of what fuel your competitors have on the market at any given time and place too, so the above algorithms might only serve to let you know how much money you make or lose per bbl, since the final cost is also the result of competitive factors combined with the fluctuations of market supply and demand.
Now don't forget the taxes.
Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus
