It does seem expensive, but if it wasn't, then there'd be more temptation to simply white-label Kagi via it's own API while undercutting Kagi's own plans.
That's actually not so bad. That company reselling Kagi search is also replacing e.g. Kagi support, so there is less pressure on Kagi staff.
And honestly, anything that gets more people into the idea of using not-Google for searching is good for Kagi - even if it is to an ostensibly competitor.
And honestly, anything that gets more people into the idea of using not-Google for searching is good for Kagi - even if it is to an ostensibly competitor.