The black market today will not be the same people. The good people in the black market will not be able to do the same thing in a SHTF times. Criminals will see the money that they can make in the black market and will take anyone that is in there way that may undercut them.
Some in the black market today have a network where they get there supplies from which will end in a large SHTF time and will be out of the business. Many criminals and gang member that run the drug & gun running business will be in charge of many of the black market. You will have a hard time showing silver or gold to buy there products without getting hit going back to where you live.
Even the good guys will have to deal with the criminals and gang member to get supplies and maybe hit them self’s. It will be a mob type of business.
I say store and prepare now so you do not have to deal with them.