People still prefer the lower entry price rather than a good bundle.
Unfortunately, it's not something Sony is willing to do until productions costs drop enough, and a good bundle/added perceived value is about all consumers are going to get.
A $350 price point would only be to prevent cannibalization of sales due to a lower 360 if the current price drops consistently succeed in doing this.
Otherwise, Sony would do well enough to hold off on price cuts until next year, dropping to $299, lower production costs permitting.