I will say that I have before been quoted a price in BZD where they later they tried to charge me in USD. The first time this happened I just paid the USD total, partly because I was naive and partly because I generally give people the benefit of the doubt and figured I must have misheard.
When it has happened since, I have refused to pay. One of those times, they ended up giving it to me in BZD when I was walking out and at another time they let me go. I'm not saying that this is a frequent occurrence on AC, but it is something to watch out for. I certainly have places I won't return to for that reason. Taxi's are the worst for this IMHO. What is really irritating is that I'm a big tipper too, but if you are going to try to screw me on the price, don't think you're getting a tip.
My recommendation is to take the name of the person who did it and approach the owner if they are there or post here asking for contact information of the owner. Odds are it's not the owner pocketing the extra and they would be interested to learn about the problem.