Bad parts on a bike can be a safety risk and so far, I haven't heard of injuries from turntable use.
He's not paying someone to install or make a dust cover- there's the difference. He can use this and patiently wait for a better one, or not. If I leave my customers with a bad looking installation, they'll have to wait in order to beat me to a pulp, after myself. I couldn't do that and whether I'm installing or even borrowing a tool, I was taught to return it in as good or better condition.
WRT fit & finish not being a casual afterthought- go ahead and tell any manufacturer about that and see how long they laugh before ushering you to the door, or hang up.
Unless big money is paid and guarantees are specified in writing and other forms, from a company that is assured to stay in business (yeah, I know), exceptional fit and finish have become rare. It can happen, but it's pricey.
I had a run-in with a "custom" cabinetmaker several years ago. I was at the house when he measured for the cabinet that would house the tuner, turntable, DVD/BD player, etc. Because the cables were bulky, nobody wanted to see them and the base moulding prevented the cabinet being pushed against the wall, I asked if he could install the back a few inshes ahead of the sides and top with the rear edge of the bottom flush to the back and the sides with dado cuts for the back- his response was "I have no idea how to do that". The description should have told him everything he needed to know. I also mentioned that the house had settled and the left rear corner of the floor was at least an inch lower than the rest of it, so please install an adjustable foot that can be accessed form inside. Crickets. Then, he sent someone to install it and the bottom drawer was too low, so it scraped as it closed. He also couldn't be bothered to use screws of the correct length for the drawers. I raised the drawer and cut the screws to length. I also built a Maple shelf to match the others with a raised edge and ball bearing slides, for the turntable.
Cabinet boy's wife is an interior detonator and he gets a lot of business from her. Not sure she looks at it, but.....