Why is programming for HD consoles so expsnive?

[NJ5]

Groucho said:

If you're talking about JRPGs, there's honesty not a lot of extra engineering work to be done for a HD console, as opposed to the Wii or PS2. If you're talking WRPGs, where you can fiddle with the environment, and the world is open, there's a LOT of extra engineering work to be done on the HDs, merely because HD WRPGs (e.g.: Oblivion, Fallout 3) are really ambitious.

If Wii RPGs were that ambitious, they would require just as much work... maybe more, since meeting that kind of ambition with lesser hardware would entail a lot of low level engineering work.

But according to Capcom they moved Monster Hunter 3 to the Wii due to high PS3 development costs.

http://www.gamesindustry.biz/articles/high-ps3-costs-prompt-capcom-to-move-to-wii

PS: RPGs are not really my thing so I may be committing some mistake here in assuming this is a JRPG.