One solution that I implemented in communick as an attempt to solve both cases: sell group packages. Let one person pay for a group of 5-10 people. This way you can still have a monthly subscription and you lose less money to the payment processors. I was also hoping that would help with network effects, as it would be an incentive for one person to bring others along. Alas, I think I am the only "customer" from my own service that has been using this functionality.