I guess I'll chime in since you wanted more retailer perspective.
I'm the Product Flow Supervisor for Circuit City in Clarksville, TN. We're a micro store...so our numbers appear smaller, but are reflective of our company as a whole. Just for numbers sake, the average Circuit City store carries about 30-40 of a particular console. Larger stores carry up to 55 and my location typically has about 15-20 in stock at a given time.
Concerning retailer profit on consoles, attachments make the most money. Of the three, the order of attachment sales is as follows: Wii, 360, DS, PSP, PS3. The Wii's success in the department can likely be attributed to the fact that most people buy it intending to use it with four players and the fact that the Wii controller is actually two different attachments.
The 360's customization focus, market place points, Xbox live cards, as well as the new black accessories makes up most of the 360 attachments and secures a solid number two spot.
The handhelds hold down the number three and four spots because of the sheer amount of accessories it has. Screen protectors, cases, and stylus pens are the majority of sales. Gaming-to-go requires more ways to power and protect your investment, so sales are usually strong. Most attachment's are purchased at the time the unit is sold in the form of a value pack.
The PS3 up until recently didn't really offer much in terms of accessories. Most buyers seem to do so with the intent of playing alone or online. This severely limits the amount of sales, because all you need is right out of the box. The biggest pitch is cables since standard AV cables is all you get.
At Circuit City, the attachment we make the most money on is our City Advantage Protection Plan; particularly at my location. We offer two types of plans...both of which last for two years. We have a regular protection plan which ensures it will work like new for the next two years under normal conditions. The other is an accidental damage warranty which protects against anything ranging from spills to sand damage. The latter, we sell plenty of on our consoles because most of our customers come from Fort Campbell, KY and they wish to take it with them to the Middle East.
Most of our protection plan sales come with the purchase of handhelds, but the Wii isn't all that far behind since the protection includes the controller as well.
More on actual console sales to follow...