David Blaine's Gaterbacks sell easily at around the £20 mark. However, as far as I know, they aren't marked, they don't come with any gaff cards and other than the foil backs they aren't custom or even on a rare card-stock.
As a fairly new magician, I struggle to understand why such playing cards are as expensive as they are! Fontaine's are very limited, hence their price... are gaterbacks also very limited? What's so special about them?