The idea is that ICE (gas/diesel) prices take some very non linear jumps and drops, and at least locally always changing, the one way it makes sense to compare with my other vehicles on what it costs to drive any particular day.
today:
diesel now $4.00
premium $4.76
regular $3.96
I posted prices just a week or so back and the premium is Up
I do not think they are done raising fuel prices, Yet.
At least the KWH price has had only a few small increases over the years.
Crazy, my street bike costs about $10 to go a hundred miles now. The Y will cost me about $3.50
and the RAM diesel about a 20 dollar bill.
If gas drops drastically then I will just refigure using the new numbers.
It just makes the most sense to figure out how the numbers work out where you live, instead of what the Gov or Tesla uses for their approximations or averages.