We almost had an international incident at my work yesterday and the customer was British, I was the American one (on the till).
A bunch of vintage sewing patterns were donated, they are all from the 60s and 70s. I put 99p on them all, but really should have made them £1.99. A woman came to the counter with one and said, "You do realize these were only 40p originally." She did not seem in any way light-hearted or joking about it. Of course I realized, I was the one that priced them up and left the original vintage price tag on them because it looked cool, and well, vintage.
"Yes, I do realize that, and it only costs a pound now which in light of the fact that the original price was at least from 40 years ago, I think it's a fair deal."
She was not amused. Naughty me thought she had already left, and so I turned to my volunteer and said, "*Lots* of things only cost 40p in 1972!" The lady heard me and said sourly, "It was a joke."
I still don't think it was.