crap what the hell was i thinking...i want to change my answer to what signmaniac's minimum is.My minimum is a case of Heineken.
Let's say we're are pricing cut vinyl letters. Our minimum is 4 sqft and they order 2 sqft.
Do you tell them they can get two of what they ordered for the same minimum or do you just quote them the full 4 sqft price?
I don't use my plotter much but, my rule of thimb is to charge them for the full price whatever it may be. If I can fit extra into it, I just surprise them when they show up. Makes for a happy customer cause they feel like that gotta little extra free. It also doesn't paint you into a corner if you can use that same space for another paying job and double your money on the same cost of materials.