Set in the wall next to the door was a small card reader.
A simple card reader would cost a merchant less than $200.
Click below for a video of the card reader in action.
There were no card readers at the metal door we approached.
The card readers display the number of credits required to play.
The "card reader" was found to be an empty plastic box.
Select this link to see the inside of the card reader.
Mounted on the wall at waist level, next to another security door was a small card reader.
"The people in the hotel wouldn't give me a key to your room so I came down here and fooled the card reader."
The seller must have a card reader set up in order for such purchases to be made.