There are ALWAYS a handful of bad apples at every show I have been to. I have even heard them refer to some games as a "show game" Typically they look for a crappy EM they buy for $100-$200 bucks just prior to the show. They get the flippers kind of working and bring it.
It gets them in for free and any party perks. They try to sell it in the first hour for $400.
On sunday they just look for the cheapest deck on the floor and buy it for $200.
Rinse and repeat.