What is a fair price on the whole system? Head unit, amps, and speaker box. Also if installing this in a car with the Shaker 500 is a completely different wiring harness needed?
The first question is like you said the wiring.
Secondly I wouldn’t give $1 for the head unit considering most people these days want Android Auto or Apple Car Play.
I’ve seen the sub and amps with bracket selling for as low as $300