Furthermore, why is HD media necessary for next-gen gaming? The truth is it isn't. You can get everything you need for next gen gaming with $299, and you can step it up with perks (which, I might add, were available last-gen as well) for $399.
Or you can try new-gen gaming for $249.
If you want an HD movie player though, yes the 360 will cost just as much as the PS3. But you HAVE THE OPTION. Remember, this is a GAME console.
Wasn't MS doing the big 'only HD' type advertising thing when the 360 was released? Only logical that sony hook onto that, especially given their TVs et al (and the Bravia is a gorgeous piece of kit, just overpriced).
HD media is an interesting one.... on the one hand, the PS3 is most definately a Trojan Horse for Blu-ray
and there's no immediate need for it. However, it's also worth noting that modern games tend to be rather huge once installed - Flight Simulator X is apparently 15GB - and that size is simply going to increase overtime (in much the same way as early PS2 games used CDs and now we see DVDs completely filled). But then you have another layer of interesting complexity on top of that in the form of compression and procedurally generated content.
Truth is, of course, you can get everything you need for 'next gen' gaming for less than $299
depending on what you define next gen as. If it's the Wiis' control method; $249 (I think?). If it's the 360s horsepower and (established) internet connectivity, it's $299 (plus perhaps some optional bodgins). And if it's the PS3s arguably greater longevity, HD movie playback (which some people do care about, certainly the lack of it was attributed as a failing of the Gamecube) and, um, ability to function as a fallout shelter once hollowed out, it's something ludicrous.
(to be fair, I've heard a fair number of positive reports about the PS3 as a console; the impression I've been getting is if it was $100US cheaper, it'd be a front-runner ahead of the 360 simply down to brand power and the 360s continuing and surprisingly poor* sales)
*less sales than the original Xbox in the same time period and still being outsold by the - obviously differently priced - PS2 in the US, I believe.