A very popular exercise, found often in the vicinity of convention centers, is the Left-Handed Price Gouge:
I have arrived at conferences a few days early, eaten in some of the local restaurants, and then gone back DURING the conference to find that the menu has been reduced to just a few items — called CONFERENCE SPECIAL MENU — and prices jacked up by anywhere from $3 to $5. Which I found rather offensive, seeing as conference people are often a captive audience, there more or less against their will (if you’re in academia where any research component is expected, you have to go to conferences from time to time) and no, almost no one has an “expense account” any more, so most of us are paying for meals out of our own pockets.
Of course, they’re counting on people not checking those prices in advance. And if the conference is held in the Big City, folks from smaller places are expected to conclude that hey, that’s just the way things are priced in the Big City.