lol, well for a cheapie, you could always calibrate it in dollars instead of gallons I suppose
figure out your MicroSec/Gallon and multiply it by the price of a gallon and just set it up that way. Then MPG would read Miles per Dollar, GPh would be Dollars Per hour, and the gallons used would be dollars instead.
But yah, just focusing on an instant value might give you the wrong impression (ask a P&G er)