I had a few subscribers, but not enough to say "Yes, this is the way forward". All in all, I made £160 over the two months but almost every user cancelled their subscription almost instantly after paying.
The support time of explaining to people it's a subscription (even though the chrome store handled billing) & handling refunds was a total time sink. My plans of spending my time developing the product quickly fizzed out as after dealing with support, I didn't care for making any changes to the product.
But, I did learn that people were willing to pay for the extension & I had an inkling that a single payment would be easier for customers to grasp. So I experimented with pricing and landed on a sweet spot of $3.99.