Dealer Discount

Not when you consider the dealer has a LARGE overhead, pays taxes , has a family to support and likes to eat himself etc , etc .
Did your brother work for free ?

Most people don't have the first clue about business. They're not making $10K on a $20K pair of speakers.

Out of that $10K they have to pay for: 

Facility
Wages
Utilities
Taxes
Insurance
Business machines/computers/supplies
Web site
Marketing

Plus they may have to pay to be a dealer and/or for training, going to trade shows, etc. 

Benjie.
Even if those figures are correct you are conflating GROSS profit with NET profit.

A HUGE difference imho.

What is so "sacred" about high end audio equipment that it should be exempt from a break in price? Televisions, computers, appliances, cars, lawn equipment, clothing - even groceries: I look for and expect to get some kind of deal.

Nothing is sacred, but who has ever walked in the grocery store and asked a cashier 10% off lettuce or milk? I doubt it would fly at my local farmer’s market although I never thought of trying.

Why does it seem that asking for discount is expected? Why not just ask what the price is and accept, or not? What the heck, just buy the lesser model and no time or energy is wasted. That may be worth 10% right there. Does everyone really enjoy negotiations?

Can a discount be expected? Possibly, when you consider a product that will enlarge a hole on a LP, and is nothing more than a plastic handle with a drill bit glued into it, and sells for $60. Just say'in.