We checked the price page and understand the differnece in support and some technical features between Pro Account and Business Account. But we do not understand if the price ist dependend on the traffic amount we have???
No there is no charge on bandwidth with Cloudflare, regardless of the amount of bandwidth you are using. There are products likelike Argo Smart Routing, which is usage based and come at a charge, but these features need to be enabled separately from upgrading to business plan.