Back in 2000, when I was a young engineer just out of university (and somewhat naive), I was on an AA overnight flight JFK-LHR in economy. At that time I'd never flown business class, and didn't know how much it cost. As I stood in the check-in queue, I decided to ask how much it would cost to upgrade. I was guessing somewhere between $500 and $1000, which would have been too much, but I was curious and asked anyway. The conversation with the check-in agent was:

Me: "Just out of interest, how much would it cost to upgrade to business class?"
Agent: "That would be twenty five, sir."
Me: "Twenty five dollars! That's a bargain. I'll take it."
Agent: "No sir, twenty five HUNDRED dollars."
Me: "Um, I see. Maybe not then!"