What are unique ways you measure customer love? ❤️

At my startup, Topknot, we've been running weekly hourlong sessions called Topknot Time since May. Since then, I've been told by ~10 members some version of they arranged childcare to be able to attend. For a session that +/-$5 (we charge $19/mo), that seemed like a big investment to make. Turns out that the people who ensure they have childcare so that they can be fully present in our sessions are some of our most enthusiastic fans.

That got me wondering: What non-traditional metrics do others use to show customer love? (Bonus points: Have you used any of them with investors?)