The federal reserve.
To make the cartel worth it you gotta hold it. So what I mean by that is, if your gang holds drug for 3-4 hours a gang might finally contest it when you are doing x/y/z with your gang. In that time frame you could make it worth holding. Additionally, the reason gangs made so much off the cartels back in the day is for two reasons, number 1 they held them for at least 8 hours of the day. The second reason is that there were gangs that would encourage people to run meth under their protection, and effectively gave them the ultimatum that if they didn't run meth when they had the cartel they weren't gonna run meth at all.