While you might be able to reduce costs through dedicated services, it also means you are going to have to write more code, maintain it and also maintain the ma

While you might be able to reduce costs through dedicated services, it also means you are going to have to write more code, maintain it and also maintain the machines etc. Don't underestimate that there are significant costs to do this reliably and maintain it over time as things grow. If you do need to do it though, I might suggest trying at least at first to use a csync2 with lsync on linux to manage the distribution of the files across the machines. We use this even in AWS for a site and it works really reliably, quick and was easier then managing a distributed FS. But before I would go that route I'd probably first try setting up a proper CDN for the images and take advantage of the caching settings so you can reduce your S3 bandwidth charges. Also, if you don't already have it, I'd also setup some monitoring on your AWS account to give you a weekly update on account charges & usage so you can see what is going on.