In general, 95% of users in any site are passive lurkers. So that leaves Hacker News with 250k active monthly users that comment and engage (which is likely still a massive overestimate). Of those, in the wide variety of comments and discussions, complaints about search and google in particular are again about 5% at most (being generous with numbers once more). That leaves us with 12500 people on HN who should potentially pay for Kagi. Seems like four times that many are doing it by your numbers.