It doesn't matter HOW the shop breaks down the cost, but a "professional" installer should be able to knock something like this out in a full day or a little more. I've done similar work in my 1 car garage working 3 or 4 evenings after work for 2-3hr blocks with way less than ideal conditions/tools.Even at 20 hours which is a lot more than what should be needed the customer's paying $95/hr.
That's an experienced design engineer's money, not "Hey, put some tunes in my car" money.
If you run a shop and this sounds justifiable to you I would say you need to get your costs down or the market will do what it does, and you will go away.
Hopefully, in this particular case the shop quoting $1900 was just SUPER busy, and shot 200% or 300% more than it was worth because they really didn't need the extra work. Given the season, that makes sense to me.