If you look at the iPad, ignoring the legacy iPad 2 (which I presume sells mostly to educational institutions) the replacement of the iPad 3 was with a “bracketed” portfolio of the higher-priced iPad 4 and the lower-priced iPad mini. Note also that the mini reflects similar pricing to the legacy iPad 2.
My second assumption is therefore that the 5S and 5C will form a similar bracket as the new iPads did. I also assume that the iPhones 4 and 4S will be retired. This means that the 5C will take up the trajectory of the 4S while the 5S will take up the upper bracket around $650.
Right now the iPhone 4 sells directly from Apple for $450. I think that’s a bit high for a ‘low budget’ phone, but then again, Apple never does cheap. However they could just reduce the price. It doesn’t have to be $450 if they can clear the same margin with supposedly less expensive materials. This is going to be an interesting one, but, the way the company reveals its sales figures, we may never know the breakdown of how many of these ‘5Cs’ they actually sell.