Many moons ago, I used to work for an auld fella. Very likeable guy but a bit of a cute hoor, as we say in Ireland. That is to say, (more or less) a rogue with a chip on his shoulder and a very long memory.
Lads would come into the shop. Many of them liked to haggle, which was expected. Some of them would try to get one over on you. In every case, Jimmy (that was his name) would always make a bit of a crack out of the haggling and let on he was losing out (he never did). As they went out the door, he'd joke with the smiling customer who was sure he'd pulled a stroke, "don't worry, I'll get you back and you won't even know you've been got".
It took me a long time to cop what he was doing but as soon as I did, it was impossible not to admire the way Jimmy worked.