The dealer who said they'd lose their Scion license if they sold above or below MSRP was lying.
The problem is from invoice to full sticker price there's only about $1000 in profit in the car. There's simply not enough room to negotiate and make money.
It may not be such a great deal price wise to buy the accessories from them. What they do is buy them from a manufacturer and marking it up over retail. You can buy all of the products (except the actual TRD stuff) over the counter for MUCH less.
However, the nice thing about buying the accessories from your local dealer is you can include them in the financing. Sure, you may pay a little more but you don't have to front the money.
Alan