They probably haven’t updated the page. This blog post says:
With new search sources proving more cost-efficient, the improved efficiency of our infrastructure, and the broader market embracing Kagi, we can again offer an unlimited experience to a broader group of users.
So it sounds like they have made lots of efficiencies to make it cheaper per search. I’m sure more subscribers helps as well.
But I’m really curious about the “new search sources” part. Where do they source their searches from?