It varies by manufacturer but typically it's some number under invoice.
When I bought Toyota vehicles it also included a coupon for 50% off accessories, like a roof rack or cover, up to $500.
Again, this totally varies by manufacturer.
I have used Costco on Toyota vehicles in Minnesota. The negotiated pricing was like $400 below invoice which was better than I could get anywhere. It depends on the location but Costco generally only has one "local" dealer as the Costco dealer.
A local Ford dealer I talked to recently said...