When I was an estimator/job-planner my company had a policy of sticking to the estimate/quote price every time unless it was extremely obvious that we were going to take it on the chin during the preflight stage.
I lobbied extremely hard and got this changed to the first production only. When accounting processed the order a "correct" price based on the actual job report data was printed on the invoice then discounted to the quoted price. Subsequent productions were adjusted to a "correct" price. This worked well for 80% of the customers. The 20% that it didn't had a complete disconnect between accounts payable and the purchaser. I was really shocked about the disconnect between purchasing and accounts payable.
extra thoughts:
I also (unsuccessfully) lobbied to blanket ban all line item charges on estimates and invoices and only provide a quantity and final price. I've always believed that your cost structure is really irrelevant to the person buying or paying. They don't have a stake in what it takes you to produce product X only what it will cost to produce 500 units of product x.
In the sales meetings I had to attend the constant complaint from sales was the sticker shock from line items for "preflight time", "proofing materials", "cutting and stamping tooling", etc. Yet somehow they wouldn't even test my idea of hiding all of that into a total cost.