Indeed. A comment above also estimated sub money to be ~1/4 of streamer's earnings, but as you mention that can vary quite widely, and in my experience it does quite so for female streamers. Pre-OF sex work is quite a lot like that too, you generally have a few whales making up ~90% of your revenue on cam sites, which is not great. On Twitch too, in my experience looking at "top donators", it's usually just a few handful of people giving big sums to female streamers.