The customer who paid once and changed how I think

A person bought my product a year and a half ago, paid once, never upgraded, never asked for anything.

Then they emailed me out of nowhere with a detailed explanation of a problem they had solved with it. Something I had never thought it could do. They had built a whole process around it and wanted to tell me.

It changed nothing about my metrics. It changed everything about how I thought about the product.

I had been measuring the wrong kind of value. I was counting upgrades and renewals, and here was a quiet person who had gotten more out of my work than anyone, and it never showed up on a dashboard. The story they told me is the story I now use to describe what the product is for.

Do you know which of your customers actually get the most out of you? And are you measuring it in the right place?