People focus too much on media cost in my opinion.
Find out your hourly cost to operate, including overheads, / rent, etc. your ink cost, and your material cost.
Convert that into how much it costs you to print a linear ft of media... Take that value and decide how much profit you want and can get. In some areas you can double.. In some you can triple, and in some Joe blow across the street is making pennies an hour and screwing up the market, and if you go too high you won't get any work.
Whatever you do, never go below the cost you figured out or you lose money and will be out of business like the guy across the street.
You want to charge as much as people are willing to pay. If it costs you a dollar, but theyre willing to pay $100.... Would you still sell it for $2?
We have a customer who manufactures airplanes and does all the warning labels on them. They just gave us an order for 15 different decals - 1x3" roughly....maybe $10 in material and an hour to set them all up, including print and cutting them... They paid $90 per decal. They have airplanes fly.in from across the world that need to be retrofited in 12-24 hours based on the airplanes specs. The decals need to meet certain FAA standards, such as size.. Color... Durability, etc... They're more than happy to pay such a high premium knowing we take care of everything, double check everything, and make sure they get their orders perfect and can count on getting the best quality and everything right the first time.
Then we have some customers who cry and say $700 for a design and 8 decals installed on their vehicle is too much, then go across the street to the guy using calandered vinyl, who slaps their decals on so crooked you can see it from 20 ft away.
Then there's some jobs like weeding small 1/8" text vinyl that we charge a "pain in the ass" to do fee.
There's waaay to many variables to have someone tell you what you should charge and base your fees on.
Check out signcraft. It's a good starter guide for how to price your products based on averages and how to calculate what you should price them at based on your costs. Some stuff is in line with what we charge... Some is way more, some is way less. It's a good read none the less!
https://www.signcraft.com/sign-pricing/