I think the OP's point is the cost of infrastructure means that this space on the market will never be less than the cost of S3 or local storage. So why buy the

I think the OP's point is the cost of infrastructure means that this space on the market will never be less than the cost of S3 or local storage. So why buy the "free space", which leads to the bigger question. why sell it. Because operating a node for File Coin is certainly not free in terms of network costs and requires the opportunity cost of giving up your local storage for the duration.