What's machine time ??
Let me guess, that's the term you came up with which includes your insurance, electric, heat, A/C, mortgage payment, water bill, food, licenses, taxes and other overhead costs.
You wanna start somewhere ?? Start by being honest and not trying to ruin the industry.
What's that you say ?? One person can't hurt the big ol' sign industry ?? Ya gotta start somewhere ??
Ya know how many hacks are out there lowballing, undercutting, selling wrong substrates, wrong materials, installing wrong and causing this industry lotsa headaches and higher costs to do business to make up for you wannabees ??
If ya got a job in a sign shop, you could learn about 98% of what it takes to get started on your own. Wanna just jump in and cut others out of the picture isn't very nice, if you haven't a clue as to what you're doing. Working out of your basement, kitchen, uncle's garage.... or wherever doesn't give anyone the right to scam customers.
If you can't figure out a simple mathematical riddle, how do you expect to figure out the business end of things ?? By simply coming on a sign forum and just throwing numbers around.
$15. is way too high for what you gave your cusomter. You should be around $2.75 each and be glad if they come back.