in the legal industry, and possibly black market, I wouldn't know, manufactures, aka, distillers, are the ones who take the biomass(cannabis trim,flower, keif-anything with trichs). Unless it is a vertially integrated company, the distillate then gets sold by the kilo to distributors who package and often brand the product as well. If ther is a good relation between the producer and the ditributor, or a lot of pride taken in the process, these will often be called "collabs". These distributors, who then sell the packaged and branded product to licensed retail stores, will either buy the distillate and make the different blends theselves, or buy premade blends. It will vary from company to company.
If I had to guess just based on the number of knock off empy carts with packaging, along with tools to fill the carts sold at places like smoke shops, I'd take a wild guess and say something similar is happening on the street. The big difference being verifible COAs(lab tests), so everyone is doing mostly the same shit they would do with any other street drug- does it look like it? does it smell like it? does it feel like it? does it taste like it? And probably more than that, "my source is reliable and trustworthy,s/he would never do something dirty like that"- and many knowingly wouldn't, problem is, most are guessing or taking someone's word, then repping it like it's the realest out there. Then again, not a whole lot different with flower or concentrates on the street either...
EDIT: Kilos of vape liquid like honeycut and terpene blends attempting to mimic cannabis flavor profiles are legal and readily available at the same smoke shops and online as well, jsut like the carts with the fake packaging from china, tho I think many of these terpene/vape companies or US based, just the hardware and packaging to avoid IP and copywright laws from china, is my speculation.