There's the general monthly vtubing expenses + gacha budgets every member gets. Kanna's is $300 + $200 according to her, given that she'll be one of their highest earners that's probably a larger amount that for most of the others, but when you multiply it by 11 members it starts adding up. Not to mention their clippers, even if you hire SEA people to work on those they're still putting out daily shorts and long-form clips on most channels.
Plus they do have managers, I don't follow the older gens but the Outbreak girls have talked about theirs a few times in their collab streams: She's apparently an MBA type with no previous experience in the entertainment world, but who's adapting well and is nice to work with. Kanna also said she's getting one in the announcement.