Looks like you never ventured into how these shops operate and where their profit margins are from. A majority of their business is wiring remote alarms and tinting. Then its easy simple installs along with overcharged prefabs and marked up prices on mainstream brands or cheap low overhead high marked up junk that the average joe might have heard of is the main cash cows. The average joe wont know anything about custom enclosures or anything else. They just want some bump* a majority of the times.
Just imagine the most ignorant close minded noobs we've seen on this forum now they will be 90% of your paying customers. The other 10% will pay for quality. However a t2 16 marked up to 1500 dollars vs 600 at cost already makes more money than a custom enclosure + sundown sub combined and its an easier sell to those rich ignorant noobs that recognize the RF name vs sundown. Of course they will also want to match the brand name with the amp which the store can also horrifically mark up.
However it does not excuse the owner from acting like a complete POS.
Oh, I know how many shops operate these days. One of my local shops has gotten into the sunglasses business...yes, sunglasses. They have a huge display of Oakley's and other high dollar shades now. It's located just beside their "demo room" which is basically a glorified broom closet.
But, any respectable shop will still be willing to do custom work for a price. OP's boss doesn't sound like the type who would even be interested in talking about a nice install. In fact, with that mark up it's hard to figure how the shop sells anything. Especially when you can shop for a better price online. Sounds like their only concern is separating people from their dollar. Instead of building a customer relationship for life the shop owner is happy to get what he can, while he can.
Which brings me to the next question...
OP, you say you need this job for money to pay bills and I certainly respect that. But, as a new employee with limited experience in car audio, I can't imagine you are making a lot of money. So, what are your career goals? Do you want to learn the business and someday open your own shop? Or, are you just interested in one or two aspects of car audio?
The reason I ask is that retail in the brick & mortar setting is a dying sector. Especially aftermarket car audio. It's such a niche market anyway plus, more and more dollars are being spent online. There may be some value in installing remote starters but, soon most all vehicles will come equipped with them from the factory. I just hope you will give some thought to your career 5-10-20 years down the road.