I don't know anything, but...
For one, as was said above, consoles are AFAIK distributed pretty close to MSRP. There's not much point to discounting if you are going to be taking a loss. Most other electronics are distributed at far less than MSRP, and with stuff like big-screen televisions, not in large quantities, so to keep the products moving there needs to be a degree of discounting.
For another, I'm sure retailers are loathe to upset the manufacturers. It's been my experience that consoles and mp3s players (or CD players, in the past) tend to move a lot more than big electronics. You don't want them to pull their product from your shelves because they're upset you are undercutting them (likely the scene with Apple). So you stick to the retail price.