What is the catch? They are REFURB's in fully working condition with a 90 day warranty!
The good point is they still have AMD rewards, so GOLD with 7950 and SILVER with 7850. That means sub £80 for a 7950 and sub £50 for a 7850!
Bear in mind the equal card to the 7950 is a R9 280 which are £150 new, so the same performance for half the price with a warranty!