In fact, I'm easy about it (my NYC T-3 electric had a long and difficult birth, but I stuck
with it), and I do not mind a deadline sliding once or even twice. The T-3 did that and
more, along with a large price increase. So, I've made my bones, there.
Customer and retailer each owe the other reasonability; do what you say that you'll
do - both of you.
That part I bolded, IMO, alters the original commitment.
You signed up for a given price for a given item.
You don't say what "large" means ($100? $200? $500?), but that in my eyes calls the whole deal into question.
If I sign up for a pre-order for $500 for an engine, and I hear from my dealer that it's actually going to be $800, the deal is probably off. (I know there have been a few cases of misprinted catalog prices over the last few years, but I think the companies that had that issue issued a correction with apology before pre-orders were actually due)
Luckily, I think you hit on a very uncommon scenario here, unless it's common in the world of brass and I am just not aware of it.
-Dave