It was maybe $50k in hardware at each site.

They operate a bunch of cellular modems that send SMS spam, receive SMS verification codes for creating fake accounts, and use the data to act as proxies for web scraping and other nonsense. It isn't criminal, but it isn't exactly ethical either. But it is profitable.

You have to go swap out some of the SIM cards every day to get new numbers, so you need to balance spreading your locations out across multiple cell towers for throughput, but also needing to be within reasonable travel distance.