And after they sold everyone one card, people are considering switching from old cards to new cards, adding a 2nd card, man the person in charge of marketing at the GPU section needs a raise and a new job, work on both sides, so the CPU's can be sold like this too.
It's like AMD's always one step ahead on GPU's nowadays. After the long reign of the 8800 GTX, the king has died and the new generation is kicking him left and right.
AMD realised that the cost of new cards was the biggest issue. Except for the few enthusiasts, most people rather pay less and save money to pay the bills or get another piece of hardware extra. Better buy a 4870 +SSD than buy a 295. And while most games are cpu bound nowadays anyway, with very little performance gains from a better gpu, especially when you look at the cost to produce those monster chips, you realise that a 4870 is enough (or xfire it for higher resolutions).
Now to see how they'll revolutionize the scene with the new 4890.