Is there a term or expression for when something was implied to be free, only to then be charged for once accepted.
I have seen street vendors do this a lot. I watched as a gyro vendor complimented a young tourist. The teenager acknowledge the vendor's compliment. The vendor then offered him and his friends gyros, they were seemingly free due to the vendor being impressed. Once the gyros had been served, the vendor charged the teenager for the gyros. Looking embarrassed, he paid him.
I have always wondered if there is a term for this, even a legal one.