Good estimation you have, but some are not true, as some cost is bare by distributor(1,2,3,4,6,7,9,11,12,13,15) and acc shops(5,8)
2. If every amp that sold to acc shops will send back for warranty and service, then this distributer will close down within 1 month already. But this is not always happen, less than 10% on average unless that batch really have problem. When this happens, distributor will not bare all the cost, but will send back to manufacture for warranty, the most is lost on transportation fees.
3. When submitting income tax, all the items above(1,2,4,5,6,7,9,11,13,15) is put under rebate as this is the cost for running the business. My wife is doing business now, so I know it. Unless a certain distributor is clever enough to give all his money to government.
10. As a distributor, sure he will charge a certain amount of money as he want to gain first. So if said the amp after all the cost is rm400, sure he will sell to acc shop at price of above rm400 and charge transportation fees to acc shops. So the cost for acc shop will be rm400+distributor's gain + transportation. Then acc shops will sell at a price that they will not lost.