Thanks for telling me about the limitation, So I guess it requires multiple lists for those with >5000 followers.

If I can explore the solution with a trial plan and If it does what I need I feel $3 - $5/month is a reasonable fee; Latter if it has added features like UnFollow alerts etc.

I don't know who else has the need for it, But I subscribed to see the insights here and it tells me 46 views so far, mostly from US, ZZ, FR and I posted this on May 25th.