There are three possible ways of manufacturing the cases:

Sintered plastic: cheapest option for low production volume. Nylon dust gets shot with a laser until it resembles the case halves. Can be dyed with nylon dye. Disadvantage: scales pretty bad with number of units, so shipping costs from group buy proxy to you might increase the price more than ordering singles directly from a manufacturer. Advantage: several "local" services, so less problems with Covid induced border issues when it comes to international shipping.

CNCed aluminium: probably the most expensive option and most inconvenient option shipping wise. But it's metal and it looks nice.

Injection molding: Cheapest option for insane production volume, probably too expensive for low volume, I am still going to ask for some quotes though. Offers insane plastics selection from ABS, and PBT to PC and PMMA, etcpp.