To rephrase my question, was the unlimited plan not available about a year ago? Otherwise I don't think I would have disqualified kagi at the time. I recall the volume being too low for my needs, even without hooking it up to any automated systems (which for me at least, was the whole point of looking into paid search engines).
was it not available about a year ago? I'm not sure. Maybe the wayback machine can tell you. But I have a gut feeling that there is a slight misalignment between your use case and their intended use of their service :)