We also define the minimum amount of participants needed to run the course. If we wouldn't reach it, we'd refund everyone. This serves as our "proof of concept", but it's also a bit tricky, especially if you're a creator living "from launch to launch" and frankly speaking any income is good to have. We see this choice as something to be made for each individual case, and the other factors to consider are things like your time needed to deliver the course, the impact you can have with it, the experience you'll gain by delivering it and the fun you'll have in the process. If you're missing one or two people from your viability number, and there's merit in delivering the course, you can always invite people for free.