rush charge aka a-hole tax. you're paying for my sleep, and paying for me to screw up my whole schedule of things. we budget our time and money so that we can satisfy our customers needs, if you want us to go above and beyond that, you have to pay for the convenience. I think it's pretty well-known that turnaround times average around a week. I've done 24hr flips before, it's not fun but if the money is right, and you have enough coffee on hand, it can be a good way to make some quick $
I'd say moreso than the fee you stand to collect, it is a tool to perhaps lock in a new client. I just took in an order from someone who needs it by Friday, all other print houses around said no, I'm taking it on knowing that if I impress them with this now (and make future terms very clear) that I just won myself a great new client. I'm quickly learning that people who have unreasonable expectations will always have unreasonable expectations, and that even if I was able to give them the shirts yesterday they'd still be unimpressed. If you're nice & gracious and it fits in to my schedule where I might have a hole, a couple days turn-time might not even get an extra charge.