At current prices. Including regional differences. Anyone know?

idk

We dont know only MS does

I imagine it's sold at a loss, especially the Arcade.

the arcade either even or a loss, on the pro, 20 bucks or so, elite 80 bucks or so. the third year on the market helps keep costs down. they have continually posted profit for a bit now. so they may even be selling at a loss with games keeping them afloat. or because of all the crap thats in the same division as gaming, the xbox brand could be erasing losses from the surface project, zune, and various other money losing ventures

Not much, if any, given the recent price cuts. The Pro and Elite versions probably offset the loss of the Arcade model somewhat, however.

You don't know. I bet you don't even know how much MS sells the 360's for let alone what their variable and fixed costs are to produce them. 

Good question, but who knows besides MS?
I'm guessing Arcade = $30 loss
Premium = Slight profit of $15ish after "upgraded" accessories costs including the packed in games and hard drive.
Elite = $50 or more profit on over priced HD despite the HDMI cable thrown in and the bonus games.

I think they'll be ok in terms of profit till Sept of next year when they decide to do their next price cut and pack in scheme.