You can really get down in the weeds when trying to figure costs like that.
Cost per picoliter of ink per print, large coverage or small coverage.
Define large or small coverage.
Cost per square foot, per running foot of material.
Cost per minute of print time.
Cost per minute of RIP processing time.
Cost per minute of material change on machines.
Etc....
Or you can try other ways,
Banner - .17 per sq/ft
ink - .03 per sq/ft
.20 per sq/ft cost
magically wave your fingers and come up with retail at 5 dollars a square foot.
Or if you are tired of eating Ramen noodles, then $7 dollars a square foot.
You need to figure out your total costs, Rent, electric, insurance, etc... per year, per month, per working day, per working hour, in dollars, then figure out a markup that will cover those costs, and then make a profit, and make a living.
With this kind of business, you have to weigh the cost vs. benefit of doing that type of precision accounting with doing a looser type of accounting.