This is common. As new content is pushed through the network, you will pay to download it and store it on your device. When that content is accessed by another node or an end user, you will be paid for each content shard you serve.
There will be periods where more content gets uploaded into the Hive network than might be served to end users, and there will be unpopular content that gets shared more inside the network than through the network to end users.
The network economics work in your favor for popular content and for Hivers with high speed network access capability, so end users will access your stored shards more than those on a lower performance device and network.