4/5 times the cost? Good luck with that! It cost us $5K in parts alone to make custom mono block class A amps. The dealer wants 40% of the price. So if we sell them for $15K a pair we make $4K profit. WOW we are getting rich right? Selling 5 of them we get $20K. We are taking everyone to the cleaners right!
Now try selling a number of units to make $100K. Cannot make money as a company doing this. Pay some rent, a few employees, taxes, warranty if and when necessary. You get the point!
Happy Listening.