Heck just imaging playing the game with absolutely no gfx stutter!!! Heck Blighttown alone is worth the PC cost. Also its not like people are going to buy a PC just for Dark Souls so jibbering on about console vs pc cost is just silly.
When it comes to game development its all about pushing the limits, the GFX/Modelers/Animators all try to make it look as good as possible and then they need to tweak things down in order for it to work on the HW they are targetting.
ALL art assets and most game code is all developed in a platform independent environment, this means that most of the development is actually done on PCs already and then tweaked/optimized for the HW (true for both PS3/XBox etc).
In some cases this tweaking isnt enough to make it look as good as they need it and in these RARE occasions it will be targetting only one platform (its very rare though, specific platform releases are mostly due to special agreements).
Now finally, the only reason why there wouldnt be a console DLC of "Prepare top Die" special content is if the content is of a higher quality that it wont play well on a console and in which case it would require a rehash of the assets (very costly).
That said I find it very unlikely that this would be the case...