I would suggest to charge what you need to cover expenses. Nothing worse than a freemium service that has to close or everyone starts to hate because they took

I would suggest to charge what you need to cover expenses. Nothing worse than a freemium service that has to close or everyone starts to hate because they took away the free. I think you have to ask these groups how they would rather pay. For the groups that have a lot of requests, you'll have to cover expenses with other groups. Are you confident you can do that, or is $10 a fair price for each request? The more you use, the more you pay. Instead of "nickel & dime" you could always roll into a package. Bronze package gets you 4 service requests, Silver gets you 7, etc...