Instead of $X/month, which must be paid even if using intensively, barely, or not at all the service, to have $X for Y amount of "no expiration date" minutes of service. Just want to try the service, pay $0.X for 10 minutes. Really like the service, pay $X++ for 1,000 minutes and not worry about it. Of course, the minute counter would stop when going away from keyboard. Maybe even more ethical, instead of paying for minutes to pay for actions per minute, $X for 10K APMs, use them how you deem fit.