Alby, sure, but they're part of a lightning payments ecosystem that stretches quite a ways beyond Nostr, so I'm not sure how you'd classify their revenue. Nostr.wine, Nostr.build, etc. I'm skeptical their revenue is anywhere near Primal's, but without more to go on very hard to know.
Discussion
How much do you think Primal is making a month?
Primal and Alby is likely taking up at least 50%. nostr.wine and nostr.land are very close, nostr.build is somewhat lower (their free uploads are propped up by nostr:npub10pensatlcfwktnvjjw2dtem38n6rvw8g6fv73h84cuacxn4c28eqyfn34f), Satellite/Nostr1.com would benext, then Jellyfish
Which puts Primal at about 25%? That would be my guess. Somewhere between 15% and 25% by just talking to people and seeing what they are using. I don't actually have any numbers.
I think Alby is fair because the main driving force of Primal is the wallet. The client itself is on par with many other options out there. So, it is wallet vs wallet.