Prior to AirBnB property owners left their homes unoccupied while they continued to pay property tax and upkeep on them during those times. Similarly, there are people with computers powered on all day that have disk space unused while they continue to pay for the electricity costs. If you assume these are the people who are going to make up the majority of the FileCoin network, this is effectively "found money" for those folks. (Albeit probably not much money.) This might not be the way it plays out, but if it does, your arguments about margins and electricity bills are moot: these costs are not increasing after the network is connected.

edit: Also even if FileCoin doesn't throw off a ton of ETH, presumably there will eventually be a wide array of services like the FileCoin network that you can transparently trade your liquid crypto assets into. For example, consider a person who happens to have 50TB of disk they don't need for the next month but would like to perform some low latency rendering jobs on the RenderCoin network during that time instead. They could easily just trade one for the other, increasing market efficiency for those resources. This example would be a small transaction in terms of ETH, but multiply that across the entire set of all computing resources, across all services, and it is a potentially tectonic shift in effective allocation of resources.