Chatbro is optimized for high traffic volumes. When use another chats you will spend the same money to server rent.
* A site with 500 visitors per day have ~ 25 online in chat. A site with 5000 per day will cost ~ €10 a month. Only members from the web chat are counted.
For each chat, you can individually set the plan. Chatbro billing works like cloud services. AWS for example. It automatically charges your balance every hour depending on the online count of each chat. You charged proportionally to system load your chat creates.