Economics aren't based off manufacturing costs, they're based off the market worth. If people are willing to buy it at that price, and they are, then they will be sold for that price. Just because Sony sold the ps3 at a loss does NOT mean every other console has to do so.
Sony has a lot of interests other than the gaming industry, so they have a lot more to gain from underpricing a console that could push their other technologies. Sony wanted Blu Ray to win the format war, ps3 helped them do that. It also encourages purchasing Sony 1080p 3d TVs and content from Sony's movie/music divisions. Nintendo doesn't care about selling you a TV or buying the latest media, they just want you gaming.
It's a bit pricey for kids, sure, but considering how many people are carrying around 600 dollar smartphones, it's actually quite affordable in comparison.
BTW the whole "Nintendo will brick your system" business is from a retailer, not from Nintendo's official policy, so get over it already. Nintendo warns that if you mod your system, it could be bricked. The same is true for any console, messing with it could lead to bricking, and no retailer is going to take it back. The same is true for jailbreaking your phones as well, read the disclaimer, your warranty is void afterwards. When Nintendo actually bricks something with a firmware update, then you can judge them for it. Until then, they haven't said anything. And don't bother whining if they only target piracy specific mods, if you lose your 300 dollar console because you ripped off 500 dollars worth of games, I don't feel bad for you in the slightest. That's the risk you take.