When estimating a new material you can base inkCost, printTime, and finishTime off similar products.
matSqftCost = cost / ((rollWidthInches * (rollLengthFeet * 12)) / 144) <~~ this figures out the sqft cost for print materials
lamSqftCost = cost / ((rollWidthInches * (rollLengthFeet * 12)) / 144) <~~ this figures out the sqft cost for laminate
inkCost = visible in HP's web access located at the printer's IP address. Likely around $0.25 to $0.35
printTime = time it takes to print a job
finishTime = time it takes to finish out job
shopRate = use a handy dandy calculator <~~ useful for figuring out how much you need to charge per hour
shopCost = (shopRate * ((printTime + finishTime) / 60))) / jobSqFt <~~ used to determine how much a job will cost you based off a previous similar jobs.i.e. knowing it takes about 10 minutes to print a 3x8 banner at say $0.25 cents sqft in ink and then takes another 10 minutes to finish it out. I can take 20 minutes * shop rate to figure out how much money I "spent" while that job was being worked on.
Then put it all together.
sqftCost = matSqftCost + lamSqftCost + inkCost
sqftPrice = (sqftCost + shopCost) + margin <~~ I prefer margin, but you can use mark up. There is a difference
Who cares what other people charge. Charge what you need to charge to make the job profitable and worthwhile.
Made up numbers time: (these numbers are made up!)
$0.44 = $300 / 675 (54in x 150ft)
$0.19 = $250 / 1350 (54in x 300ft)
$0.25 = based off ink estimates
20min = print 5x8 graphic
5min = finish 5x8 graphic
$150hr = shop rate
$1.58 = ($150 * 0.42) / 40 <~~ based on 40 sqft and 25 minutes total
$0.88sqft = sqftCost
$4.92sqft = (0.88 + 1.58) + 50%
That would be a base price for a print/lam kit that cost about $550 if your shop rate was around $150 hour. You may still need to factor in design time, customer time, waste, etc. As well as general market value and job complexity. For a smaller job you may bump your markup/margin up 5-20 points; that way you can have room to work with on square footage discounts.
No reason to trust what anyone says about their pricing. They could be lower than what you'd need to sell it at and then you'd be out money. They could also be way higher and you'd be pricing yourself out of jobs. Then another person will likely say something like "charge as much as you can" or something along those lines. Best to just charge what you need to charge.
It'll take you way less time to figure it out then it took me to write this.