You can't find 7950's right now, and if you can they are over $500 bucks a piece.
Not intending to thread hijack here, but if this actually is the case I've got a Sapphire 7950 3GB DDR5 975mhz core 1300mhz memclock card that I'd be willing to sell. Especially if the price is in that sort of range
The card is still under warranty, was purchased in march 2013 has mined, but never continuously for long periods, has also never been overclock and never ran hotter than 69*C
The 79xx series has been discontinued, and the supplies went dry, so yes it's true you can hardly find them.. but people are panic buying these cards when they don't need to. The R9 280X series is a rebadged/better 7970 going for $300msrp right now.
MSI 7950's (the best of the 7950) were going for $200ish until they went dry. No need for people to pay crazy prices for these right now.
Can you find me 12 in stock R9 280's? Looks like your best bet for those will be early January. Wonder what the difficulty will be then.