Its not always about the assests. It about given the illusion of something being more life like or real. It requires deeper and more intricate detailing in artwork, animation, and the like which will require more time, man power and money.
On the topic of dev costs next, and dev paying excessively more in the next are just wasting their money, given that most big budget games already produce assets at a higher detail level then they end up in the game, and you hardly need to make your game world amy bigger then the likes skyrim.
I hope that the dev concentrate on using the better specs for polish and frame rate. If they can manage visuals like BF3 and crysis 2 on the PC at a good frame I'll. Be happy. Sadly the WiiU just isn't capable of that so for the time being I'm not interested. Give me a price drop. Zelda game and a 3D Mario game and I'm in, but until then I'm happy to wait.