Is player instanced housing more of a strain on the server?

[Angellos]

At times of high congestion the instance servers have occasionally become overloaded, resulting in wait times for entering an instance. I believe instanced housing would count towards that sort of problems, especially since players would be likely to idle at their houses. keeping the instance reserved.

Obviously SE would have to devote more money to upgrading their instance servers to handle the load. They're upgrading everything as we speak: And more upgrades need to come with the influx of players.