Somehow I think Microsoft purposely made faulty systems to make you repair them, so you could fork up more bucks. Not to mention, they released it early to get your commitment and to use that as an excuse for faulty systems. Not only that, but I think Microsoft released it with minimum parts, so getting extra things, like a HD-DVD drive and whatnot need to be bought seperately would add to the costs.
Sure, a basic 360 would cost a small amount, but then repairs, upgrades, etc that are essential would rack up the total costs to something along the lines of a PS3, which so far, I have not heard of that many faulties as the 360 has.