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Gura is probably #1 and even with the most pessimistic estimate no way she isn't at least top 5. Her merch is consistently best selling not just for hololive but even compared to regular mainstream anime stuff. And the estimates of her membership income were in the 6 figures monthly (granted this was from last year she may have lost members since then). And then there is sponsorships which she gets pretty regular and usually pay based on views.
>but muh superchats
Even if her superchats were $0 she would still be posting yearly income in the millions. If you have any remaining doubt just look at how much Cover favors her in promotional material and being the first to get just about anything, they wouldn't do that for no reason.
