Do Nina / Marcus / Ted essentially WORK for the manufacturers?
Why wouldn’t the manufacturers want their own machines and gear?
Why do they need middlemen?
Alternately, if Nina / Marcus / Ted are getting their items via smuggling / robbery / murder / looting, why don’t the corps stop them?
They certainly wouldnt be advertising in Concordia if they knew there were black market vending machines in town robbing them of their profit.
Hyperion certainly doesn’t like to share and would definitely have the resources to make black marketeers lives VERY uncomfortable!