You were proposing a $229 (nearly zero margin) price point which, I don't care how superior the iPad 4 might be, would absolutely draw buyers form the iPad 2 and iPad4. While profit can certainly come from volume, going from a 30% margin to 1-5% margin is never a good business plan.
Apple has obviously done the math so we're seeing the $329 price for a reason.
$229 is not even remotely a "nearly zero margin", please!! You think Kindle and Nexus are selling their devices at a loss by pricing them at $199??? Component to component all these devices probably cost the same or very very similar. There's only a delta premium Apple's customers are willing to pay (me included) for the ecosystem - $130 is way out of that range.
The ONLY reason iPad Mini is priced at $329 is because Apple's getting greedy this time around.
As for your cannibalizing argument, why don't you argue that iPad Mini will cannibalize from iPhone too, seeing a few "Can I use my Mini as a phone replacement" threads around here?