Just get the GTX 780. Though the 290x is certainly the faster card, the 780 GTX will be considerably cheaper than the custom R9 290x (if you can even find a 290x... those that you do find will be horribly over priced due to the markup caused by lite-coin miners). Plus, the 780 GTX comes with game bundles (I suggest Zotac's AMP edition from amazon--you get The Splinter Cell Collection and Assassin's Creed Black IV Flag to boot). The 290x/290 have theoretical advantages (AMD to AMD conversions from console games, more VRAM, Mantle) but those are all theoretical, whereas in the here and now, the 780 GTX is more than capable, cheaper, and comes with game bundles.
Oh, and to answer your question, the 290x lightning while having an MSRP in or around $569-$579, will more than likely be priced at around $649 as is the current price of these AIC boards.