Most responses here talk about substrate panels, so I'll answer that one first. Our internal pricing lists shows two prices for each substrate - a per-square-foot price and then a full-sheet price. The square-foot price is much higher than the full-sheet price, and depending on the size, we default to the lower number, and then charge for cutting if needed. So a 2' x 3'
sign (that we'll make using a drop from a previous job) gets charged at the square foot price, while a 4' x 6'
sign would get charged the full-sheet price plus the cut. It works for us, and as others have mentioned, jobs that use the drops are just gravy. If anybody ever orders a bunch of 6" x 96" backlit acrylic
signs, I'll make out like a bandit
When it comes to printed media, I've built an average waste factor (25%, if I remember correctly) into our pricing tables. This might not be the most accurate method, but it's pretty close and saves us from the headache of doing it differently on every job. We can nearly always nest jobs together so the waste isn't significant. And since our price reference sheets are only for internal use, we can still charge extra if we're quoting something like a 12" x 120" print on 3M wrapping film.