OK, a topic not about swapping tickets but about paying inside the Amsterdam Arena (soon to be known as the much better name "Johan Cruyff Arena").
During the last events the Amsterdam Arena is a cashless stadium. You could pay, with the shops in the stands (so if you have a seat) with the following cards. PIN (Maestro), Master Card, Visa, Visa Electron, AmEx en VPay.
On the field (so the general access area) last year during Coldplay you needed to buy an Arena card. You could buy one in the space between the gates and the entrance of the field. (you wouldn't be the f