I would go tiered. Per-chat session is great until you try to collect on someone who has a $0.025 bill. I'd start with a small monthly fee ($30/mo) + per chat

I would go tiered. Per-chat session is great until you try to collect on someone who has a $0.025 bill. I'd start with a small monthly fee ($30/mo) + per chat session. If that doesn't seem to be capturing the hearts and minds of your licensees - then go into a tiered approach for "capped chat sessions" with overages.