Pricing and specs gives a chance for Nvidia to respond,since there are no cards available from AMD now for people to buy.
ATM,Nvidia does not know whether the R9 290X is faster than a GTX780,slower or around the same speed. They don't even know the price! It also means they cannot rain on AMD's parade by reducing prices,etc,before AMD actually have cards that they can sell. Remember,Gibbo said he does not know himself the final pricing of the R9 290X and that it could be anywhere between £399 to £599,and AMD have not told him.
Also,the R9 290X cards which will be on pre-order next week are the more expensive BF4 edition cards,which again are not probably indicative of normal R9 290X pricing.
Its all about keeping Nvidia in the dark.