high quality brands produce external factories and control?

all these high quality brands like Armani, D&G, Ralph Lauren, Tommy Hilfiger... is pretty much all of their stuff made in external factories (in China, Vietnam...)? so there could be this same factory making clothes for unknown low quality brands and for couple of Armani and Ralph Lauren? do these brands hardly even have their own factories? If Armani does a order of 20 000 shirts of a design, how do they know that this external company is making 20 000 and not 30 000 and selling 10 000 in black market? what about luxury brands like Gucci, LV, Hermes..?