The big thing, (as shown by the Vita, 3DS, and WiiU) currently in the market is sustaining consumer demand. PS4 can't have a situation where the sales dry up 3 months after release. It'll be the end of it.
My thought process on the pricing:
$299 - Mass sellouts, media loves the price while finance sector questions Sony on their cash problems, Sony "buys" a big lead in the early console market
$349 - Pulls consumers in, Sony loses some money but basically "buys" some additional early install base
$399 - Expectations are met, the people who want to buy a PS4 buy a PS4. Media is satisfied with the price and the reaction is as expected. Sony probably is break-even on the console
$449 - Some people who plan on buying a PS4 don't, a good portion of enthusiasts still do, media spin is negative on the price. Sony is somewhat profitable on the hardware
$499 - Very few people buy, media destroys the console and the console is stillborn
If you look at the pricing of most of Sony's latest new tech, it tends to be at the very upper end of the pricing spectrum