i use 93 octane in Black Betty,

So the fuel costs more, but you should go farther per gallon with the SuperCharger

Fuel cost is offset by better fuel economy. I get 3 MPG better with the S/C.

Maybe someone will figure out down to the penny what the total cost difference is. Betty on regular got 13 MPG before the supercharger, and 16 after (premium). So the price difference is more than just the difference between regular and premium

Keep in mind, you will drive a supercharged jeep more aggressively than a stock unit, so you probably wont see a great MPG gain. Its hard to stay off the gas.