The biggest point you are missing here is return on investment. Your investment in the equipment and the software to run it, setting it in place and getting it to run correctly, learning to use it, keeping it running correctly and your general overhead are all items that are covered by the revenues generated when that plotter runs. Just like any employee, it must provide enough revenue every day and every month to cover its cost and make a profit.
If you were in a situation where you were charging someone with their own vinyl and operator for access to your plotter (and the computer and software to run it), what would you charge per hour? Forget the "it depends" stuff for friends and just crunch the numbers. 252 work days a year x 8 hours a day = 2,016 hours a year. Pulling example numbers out of the air, if your total overhead per year is $90K including your salary, then 90,000 / 2,016 = $44.64 per hour overhead expense. Add to that your annual profit (your salary covered in overhead) of let's say $30K per year, 30,000 / 2,016 = $14.88 and you have a price of $59.52 per hour you should charge at a minimum for the running of the plotter. Of course, your numbers will be different and there is no allowance for other equipment, but the point remains the same ... you make your money when your equipment runs.
