Got to be a shimano long sleeve jersey I picked up at the cycle show madison stand a few years back. It was on the Jersey rack for £5 but there was a sign saying all long sleeve jerseys were £10. I took it to the till to be asked where had I got it from, so pointed at the £5 rail. Not sure exactly what happened next but after at least 5 attempts for their card machine to work and I paid £3.50ish cash from coins I had in my bag…
When I got home and checked my bank statement they had successfully taken £5 three times, but refunded me 8 times!
So I had just been paid £21.50 to take a jersey!