Thor God Of Thunder :
If AMD did an R9 290X promotion where it was $300 a card if you buy two for crossfire, they would reclaim lost market share.
AMD does not sell GPUs at retail; their AIB partners do. AMD does not have the power to make sales since they are not involved in the retail pricing beyond saying what their target MSRP for a given GPU is. If individual board manufacturers want to do promos, that is up to them.
As for comparing GPU prices with i5 price, Haswell is ~180sqmm while the R9-290(x) is nearly 440sqmm. A die two and a half times as large is considerably more expensive to manufacture. A PCB with enough layers to route a 512bits memory controller is also going to be considerably more expensive than a 4-6 layers board for CPUs with 128bits memory interfaces. The video card also includes VRM, GDDR memory chips, the PCB itself and tons of extra-cost items that are not included with a boxed CPU.
For the R9-290(X) to retail at $300, someone would probably have to eat losses.