[tomxor]

You already started along the road to normalisation by using MJ/L but you might as well go the whole way and consider absolute cost per person per mile... or person miles per absolute unit cost if you prefer. Those might be more telling figures.

For instance many EV proponents note the total cost of ownership difference due to significant differences in maintenance costs. Playing the other side of the argument: they tend to forget about the value of upfront cost is more than later cost.

It's still possible to achieve some sort of quantitative comparison by applying an interest rate based on "distance" of the cost in time before summing them. If you applied this to a regular petrol car you might be able to make a better comparison to the ticket price of a flight.