That's not how the Internet business model works. Receiving data is effectively free. Transit providers charge the sender for the bitrate (high for the web host, low for the web user) and a fixed fee for the connection, which you will have to pay regardless. Peering is paid for per connection and often by the web hosts who want to avoid transit and get better latency to the ISPs customers. In terms of traffic, there is effectively no difference in cost between sending traffic internally or receiving it from an external source. The reason for data caps is that ultimately networks are capacity constrained, but mostly at the last mile, not at the peering and transit links.