yes. running a server costs money. I have lemmyfly.org running just 2 days now on digitalocean using a cheap 1GB ram, 25GB diskspace and 1000GB bandwidth for $7,- a month. Storing images on the server will eventually take up all space and bandwidth meaning you have to upscale -> pay more.
Using a different location for storing images and/ or videos is best to offload the instance !
lots of traffic on many small files eventually uses more disk space and bandwidth. Depends on the growth of the instance