I'll sometimes adjust pricing based on ink coverage. On small jobs I'll just use the high end ink/sqft cost but on larger projects it's worth having a look at actual ink consumption as it might surprise you. I'm talking the difference between some black spot text with white background vs. full coverage dark print on the whole area. It could vary from $0.05 - $0.60 a square foot.
Not saying every jobs needs to be over-analyzed, and totally agree with/like what ikarasu is saying regarding pricing. Sometimes you can just go with your generic pricing and sometimes you can price it at whatever the customer is willing to pay. Good customers will be happy to pay for the service at any cost, as long as you always deliver and provide exceptional service.
Not to go too far on a tangent, but on Wednesday we had a good customer call us up in a panic wondering how quickly we could make some
signs for them. It seems that someone forgot to order
signs for a construction project they were starting on the TransCanada highway. They're 2.5 hours away, in a different province. Their first phone call to us was at 3pm and by 6:30pm I met one of their drivers at a gas station on the highway with their
signs. We ran (4) 4' x 8' dibond
signs w/ high intensity reflective and cut vinyl graphics in the time that it took their driver to make it here from their shop, and that included me having to go buy the reflective from a local company. It was a all-hands on deck situation and involved everyone staying late but we got it done. That's what good customers want and will pay very handsomely for. Turned out to be a $3-4k job that took us 2 hours to produce, but we saved their a$$ and thanks to our efforts their site didn't get shut down. Those are the customers you want, not the ones that nickle and dime over square foot costs!
To get back on topic, we don't discuss or use flat rate sqft pricing with our customers. We know our raw material costs for everything, but every job is custom. Might take a few minutes more to quote each job but it ensures that you know you're making good margins on every project. We factor in our material costs x markup, waste for webbing, machine time, and labor to come up with our pricing.