I would happily pay for a search engine that provided good results, but seeing as it's ostensibly Just Bing under the hood, I'm not sure what I get that I'm not getting from DDG or MetaGer + an ad blocker.
Kagi doesn't strike me as a privacy alternative given that all my searches are necessarily tied to a user id which is further tied to a payment method.
Finally, the metered usage feels far too much like an ancient cell phone plan. I really hate the idea of me paying for search only to have to switch to actual Bing when I hit some limit.
I like what Kagi is trying to do, but I don't see it as either sustainable or awfully useful unless such a service owns its index.
Feel free to let me know what I missed, I'm sure Kagi's paying customers are paying for a reason!