Charge small, charge often. The EC2/Rackspace Cloud type of micropayment system is what I'd use here. Charge per chat session to begin with. Why? 1. Psycholo

Charge small, charge often. The EC2/Rackspace Cloud type of micropayment system is what I'd use here. Charge per chat session to begin with. Why? 1. Psychologically, to the consumer of the solution, each chat session seems way cheaper. Getting somebody to sign on to paying 0.025 cents a session is easier than getting somebody to sign onto a $30 or $50/month solution, even though in the end the number of chat sessions may add up in your favour. 2. Most potential value is captured. Charging per chat session takes out the hard work of calculating large, tiered pricing models to capture your consumer base. Think microeconomics: a small-time user might want to pay you $10/mo for a few chat sessions, but your pricing starts at $30/month. 3. You can always add tiers later that are based on usage by scaling down the price as quantity goes up (a traditional economy of scale.) Have somebody running through tens of thousands of requests? Give them a slightly lower price.