Ask HN: How to best monetize a Chrome extension with over 50K users

I own a free Chrome extension that has over 50,000 users and is still growing. I had been looking at this as a fun side project and it hadn't even occurred to me that I would make money from it. During the past few months though, I have received 2 offers to buy my extension. I didn't think much and believed whatever offer they'd make would just be a tiny amount because I'm not making any money with the extension, so I said no without even asking for the price. In hindsight, that was silly of me, I should have worn a more business-friendly hat.

Anyway, I'm curious why people would want to buy a free extension. Can you actually monetize a Chrome extension? I read about the Chrome Store Payment API but I still think hardly anyone would pay for an extension. I myself use many browser extensions and never have to pay for one. Does anyone have experience monetizing their extensions and how do you do that? Any advice is greatly appreciated.