Yep, just move on to the next customer, and stick to your guns. I tell them up front that last minute changes will double the price and they go to the end of the waiting list....
I worked for many years in the printing industry. SOP is to give the customer a firm quote, and have them sign off on it. That's what you're gonna get. If it goes to press and you suddenly decide you want purple ink instead of pink, too bad, make a new order next time cause you ARE getting billed for this one. By far, the majority of customers understand this and it hardly ever was an issue.
The lesson to be learned, I think, is to communicate well at the outset to avoid misunderstandings. If the customer's just a PITA after, I think a maker's within his rights to decline the job.
One designer I worked with had a triangle-shaped sign over his desk that read, "High Quality... Fast Turnaround... Low Price. Pick Any Two."