I have no idea where you're getting any of that from. How is the PPC architecture outdated when you're comparing it to the x86? I also don't know where you're getting numbers for how much Nintendo is paying for it's processor and how much Sony and Microsoft are paying for theirs.
The PPC is just an upgraded processor from the GameCube. Well Wii, which was upgraded from the GameCube. It's outdated compared to the x86. With the x86, it's much more like a PC, thus making development not nearly as bad as it used to be.
And in terms of numbers, it's just a guess. The WiiU is pretty/was pretty expensive with relatively weak hardware compared to the PS4/Xbox One. Yet it's costing Sony 380 bucks to make a PS4. Meanwhile Nintendo said that they lost money on consoles sold, and buying a game was the only way for them to make a profit.