Well in many cases, the manufacturer is providing the product free, so that doesn't affect the dealer margin. Although there is a current offer (not the Pioneer) where the manufacturer advertises a freebie, which the dealer has to actually pay for...
Plus, whatever the price of the product when it is released, initial discounts are by the retailer, hence you see maybe 10-15% discount. After the initial interest of a product has died down and sales start to slump, some manufacturers have to find a way of boosting sales - hence freebies, and sometimes reducing the rrp (and the trade price), which can sometimes look like retailers are on a huge margin - with vision products, and certain manufacturers, that's so far from the truth. If the margins were as high as some claim, there would be less store closures. More often than not, the inital trade price and the trade price near to the time of discontinuation are entirely different.