How do mushroom growing companies grow so much? I was wash mushrooms for dinner and I was wondering how...

I was wash mushrooms for dinner and I was wondering how do the companies gain so much to grow in one place if it a fungi?
Nesting Box For Robins?
Answers:    They hold huge single storey buildings in which they grow them contained by the dark contained by special compost.
What plant ?
They have mushroom houses where on earth they grow - dark cement buildings where on earth they grown in flats.
I involve to verbs my Lilac Trees and...