I am sensing an undercurrent here of something, not sure exactly how to describe it, but...

if there's an analogy in the world of competitive hobbies, maybe sort of like solar cars or land race record holders.

car audio is a hole. You dump money, time, labor, and all sorts of other stuff in, and when you actually create a finished product, it's not unlike art in a way, since it's an expression of your will, it's an expression of your acuity, your professional best, or...

your pride.

and being able to subdivide the car's value with whatever pride tacks on in your hobbyist efforts, is not that simple since the new owner can co-opt all your talent and perfectionism and ride your reputation like a scalded pig until it's obvious to others that he'd not simply bought your end game, and ran with it.

The shank is that the new owner may be under-deserving of your sweat equity, and selling such a honed bit of kit breaks that off where it'll never come out.