That's pretty close to what I'd read as well ($299 for the standard, $399 for the enhanced). I've also read that Nintendo will target theirs for around $200, while the PS3 will have two versions, one at $400, another at around $700. As for backwards compatibility, there is some conflicting information, but I tend to believe the Xbox 360 will be.
Is $400 too much? I don't think it is. A top of the line PC graphics card will run you that much. Given that these new consoles appear to be a major leap up the technological food chain from the last generation, I wouldn't complain too much about the price. You'll only have to pay it once. The games are another story entirely. If the games are $70-80 each, then I think its a problem.