I'm on the starter plan and very happy with it.
I'd love to have Kagi for my young kids but the only way I can get it would be to switch to the family plan for 20$/month. This would be a 15$/month increase for me, which is too much (sorry).
The ideal solution for me would be a capped, pay for search for my kids. I can't see them using more that 50 searches/month at the moment. I might stretch to 5$/month for 300 searches like the starter plan.
I could imagine many single parents, or parents with non-technical partners, who currently use the Starter plan would be happy to pay a bit more so their kids can use Kagi.