I would have purchased several services over the years if they had a pricing like this, which ultimately I did not (because they did not). In particular there was some video editing software for $20/mo, but I knew I'd probably go months between using it. I'd have gladly paid $20/mo when using it, but it would stick in my craw the months I didn't use it.
You don't pay some heavy license fees for a local installation anymore, but get a login where you get billed a specific amount if you use it that day/week/month etc. I was pretty sad when I saw how it got implemented...