I am totally with you. I work as a composer and have no use or need whatsoever of that über-expensive gfx card.
I would have thought most people don't.
I've never really understood workstation gfx cards in all but the most niche usage scenarios (and these are way beyond the chip quantity and thermal envelope that you get from a little can like this). The driver certification that tries to justify the extra digit on a the price tag is moot on apple hardware and as it's not windows, it's hard for a manufacturer to gimp opengl performance without being too obvious.
They're using ati chips too. They're hemorrhaging money and with their latest two generations of consumer cards, haven't bothered to do the usual product differentiating gimpage. I don't understand why anyone that really needs ggpu performance would buy anything else - The only exception being some big-corporate policy calling for warrantied environment etc (and again, who buys apple for this?).