Short Path Distillation
Short path distillation is a method of creating or refining cannabis oil into distillate and is particularly useful when you are working with smaller batches. The distillate travels a shorter distance with the short path method. I imagine this is how a lot of black market cartridges are being produced.
In this video we can see the process under way. They add in over 180 grams of wax into the heating chamber which releases the THC/CBDs into a vapor which the distiller than re condenses into distillate. It's very interesting to watch, and this is what is in most cartridges.
Cheap To Purchase
Smaller kits are relatively affordable, costing a few hundred to a few thousand dollars. This makes it something doable for a hobbyist, or a black market dealer. So it makes a lot of sense why the black market is flooded with imitation cartridges.