Of course you'd have to pay 700k if you're basically rejecting anyone who's ever been online. The candidate pool is, like, three people.

Uhh... having a LinkedIn takes like 10 minutes spent once. For most industries it's a pretty obvious investment to make yourself reachable by anyone who might be looking for you and to have an added data point of legitimacy (as in simply "is this a real human being emailing me")

Your heuristic is extremely bad.

I use LinkedIn to find jobs; and to troll the self applauding, back patting influencer crowd for fun.