I dont think it actually works that way, 290X is a brand new chip with new architecture - more transistors and processing units etc - its way more complex, and therefore harder to produce with lower yields when manufactured, more bum chips they either bin or throw away which costs money. Plus they probably want to recoup their R&D costs as well.
Your words could be true, if 290X is a really brand new architecture. But, it is not.
290X could be an advanced GCN, but not a new architecture.There are just a few developments on size and power consumption. If HD 7000 series and 270X, 280X are GCN 1.0, 290X and 260X are GCN 1.1. Therefore, R&D cost is not much for 290X and 290.
I think Hawaii XT - 290X will be 550$ and Hawaii PRO - 290 will be 450$.
But we know from Catalyst drivers that there will be also a Hawaii LE (280XT or 290LE). It may come with 3gb 384 bit instead of 4gb 512 bit. I think it will be around 350$.