This is the key right here. The builder wants what he wants, but that doesn't mean you have to agree to it.
When I found a builder I liked, I asked if he employed his own tile setters, wood floor guys and painters. If they work for him, then he pays them and there is no way way around it, however if he subs out, he is just as happy to have me contract them. Fewer bills for him to pay, but I have to be very considerate of his schedule and worksite. In a hot market builders won't let you do any of your own work. The builder agreed to let me do my own tile and counters and supply my own lighting and plumbing fixtures. I'll probably be using the same guys he would but it will cost me far less. I am able to get the in floor heat and a more custom tile layout than he would have done. Home Depot has a great website where they close out their vessel bowls and lights and other fixtures from their Expo stores. Paying cash for that stuff keeps my mortgage lower. In another time he wouldn't have even heard me out, but this is a buyers market.