Well, you pay the person organizing it, and it's not always crypto. In fact, with all the stuff I have I've never used crypto. Most GB are US based. They ones I use have been around, do these often and use big name suppliers. They will be sitting on your money for 6 weeks to 3 months. That's why it's a not I need it now or Amazon. The money difference is crazy on some of them.
This is an incorrect assumption. Plenty of well-known vendors have caught bad results from post-purchase testing and manage to flood the zone with shillery until the bad test results get forgotten. And not just under-fills. Hair and bugs in vials, vials containing the wrong substances, failed sterility, way too much of the substance on the label, endotoxins, all have occurred and eventually get forgotten.