They can, depending on how they work. If the values are being fetched from a secure chip, however, I believe it's not as easy. And as I said, even if it is copied, unless it is spent VERY carefully, it can be spotted and marked as copied.

Here's mifare desfire EV2's leaflet that talks quite a bit about the security features it has: http://www.nxp.com/documents/leaflet/MIFARE-DESFire-EV2-Leaf...