You are seeing potential price drops only from the production costs perspective, but mainly supply and demand determine the price of a product.
If the demand stays strong, neither Sony nor Microsoft nor Nintendo would lower their console prices for years, even if the production costs sink... the Wii or PS2 for example in their first years. But if the demand is weak and the competitors get more and more market share they won't have another choice than to lower the price and to hope to make up the losses with software and accessory profits.
Additionally PS4, XBO and Wii U aren't only competing with themselves but also with PC games. Yeah, console and computer gaming (both with their own advantages and disadvantages) have always competed up to a point for decades and consoles are cheaper than PCs. But how much more expensive was a decent gaming PC in the past and now? Every console generation that price advantage toward home consoles got smaller.
Someone in this thread posted a link to that picture:
So how much did a decent gaming PC cost at the same time of a console release? 2x? 5x? 10? Well, you could always buy or build PCs in very different price ranges... from entry level to killer rigs. I tried to find some middle ground and looked up some advertisements in old computer game magazines... setups they thought to appeal PC gamers of that time. CGW has a great archive of all its magazines of 25 years: http://www.cgwmuseum.org/galleries/index.php?year=0&pub=0&id=500
Naturally you could always save 10% - 20% if you built that rig yourself, but these examples are only for a general direction.
In 1986 you would have to be crazy to build a MS-DOS-PC mainly for gaming (if you or your parents needed something IBM-compatible anyways that's another story), an Amiga 1000 or an Atari ST 520 were much better choices for gaming computers. The A1000 costed 7.5x ($1300 without monitor) of a NES, the ST520 costed 4x ($800) of the NES:
In Q4/1991 a decent gaming PC with a sound card was in the price range of $2000 - $3000, so 10x - 15x of a SNES:
In Q4/1995 a decent gaming PC was still in the price range of $1800 - $3000, so 6x - 10x of a PS1:
In Q4/2000 a decent gaming PC was in the price range of $1500 - $2400, so 5x - 8x of a PS2:
In Q4/2005 a decent gaming PC was in the price range of $1200 - $1800, so 4x - 6x of a Xbox360 Premium:
So where are we now? You can already buy a PC which can keep up with the XBO or PS4 for $800 - $1200, so the 2x - 3x of the new consoles. And the PC costs will fall further the next years, so the console prices can't stand still for years. Graphic cards which can keep up with the PS4 performance already went from high end (GTX 580 / AMD 6970) to upper class (GTX 660 TI / AMD 7950) to upper-middle-class (GTX 760 / AMD 270X). That will continue with a shift to middle-class (GTX 850? / AMD 360X?) to entry cards (GTX 940? / AMD 450?) the next 2 years.
