"5000 clones is ~100 trays of 50....those 10 people would only have to make 10 trays each. Not impossible to do."
In terms of time and labor, it seems manageable, but 10 trays take up a lot of space. I'm living in a fairly spacious residence now with a big back yard and even for me, 10 trays of cuttings would leave a big footprint. Before, I was living in one-bedroom apartments for about 8 years and 10 trays of cuttings would have been too much to handle with two cats and another person living with me.
So I guess if you have access to a farm or similar setting, with maybe a barn and a greenhouse or two, you could start a bunch of clones out of sight of your nosy neighbors... but if you've got 10 human beings working as a "team," that's a lot of loose lips, potentially, lots of potential for one "team member" to decide they're not getting enough paid enough or that they dislike someone they have to work with... Inevitably someone would blab to a "friend" who would pass the info on to either an undercover cop or just some criminal scumbag who would decide to rip you off. At least that's what I would worry about... But obviously the black market operators have been making their business models work for decades, so they must have safeguards and procedures they can rely on.