I'm surprised this is still floating around as fact. Back during my earlier days as a Hololive fan I dug very thoroughly into the sources for this and concluded that every instance was a case of mistranslation or colloquial speech... except
maybe the one clip of Matsuri talking about her debut days which is far removed from even Myth-era Hololive.
Here's what I found back then:
"Everyone uses 給料 (kyuryo) when talking about their payment, which clippers always translate to salary. However the word can also mean wages, pay, or remuneration. It doesn't always carry the meaning of salary, and even then it can be used colloquially rather having the strict meaning of a fixed amount. Coco used it when talking her and Kanata's first payment, Lui used it when talking about her first pay, Lamy used it when talking about how her compensation went negative during merch production, Matsuri also used it when talking about her income near her debut. I saw one clipper translate Laplus saying 給料 as paycheck but they put salary in the clip title.
"When Kanata said she earned 20000 yen in Feb 2020, she was reading a chat message which used 月給, which does mean monthly salary. However it wasn't her words, it was from the chat message."
I'll also add that Kiara also used salary when talking about her financial issues last year, reading the word "salary" from a chat message, when she clearly meant her monthly revenue payment and not any fixed income.
Furthermore in Cover's IPO documents, and quarterly and yearly financials, there is zero evidence of any fixed income for the talents.
The only assumption I think it could be reasonable to make is Hololive
might have a small stipend for talents that aren't yet monetized. But it would still be an assumption without any solid supporting evidence.