I'm still genuinely surprised Valve hasn't launched a game streaming service. Then suggest developers offer Win, Linux, Mac, AND streaming, so they can stream to every platform (like this Steam Box) they can.
"Steam Cloud Stream?"
"Steam Cloud Stream?"
It's possible that smarter architecture could bring that figure down; OnLive needed to have a physical machine for every concurrent player (!). And OnLive made plenty of other mistakes that a smart business like Valve might avoid. But even if you did everything right it still sounds like running a streaming games service at a profit with today's tech would be a serious challenge.
It seems highly likely that the support costs for the 1,600 users were noise amongst the staff, marketing, licensing and other costs (including potentially wasteful overprovisioning based on expected sales).
Having said that if it cost even $10/month (and it may be more or less) to support a user the whole business model may break down.