I double checked because I was about to correct you, and you're right, but I could've sworn it used to be monthly (still low limit, but resets) so maybe GP remembers that too. Or perhaps it just wasn't as clear that it was a one-time trial before, and we both misread.
Looks like it used to be a free plan with a usage limit when they first launched in 2022:
https://web.archive.org/web/20221111171736/https://kagi.com/...
It’s a trial, you get 100 searches for free, then you have to start paying.
I don’t think you can call it a free tier but it’s a nice offer to evaluate the service before paying. I tried it for a bit and wasn’t happy with the search results, but I might try again though and use up my remaining searches.