I do agree that, if they wanted to get rid of their original line of business without looking like that's what they were doing, this would be the best way.
Simple reasoning will get you to that conclusion. There are no physical plants to maintain. No physical inventory to maintain. No postage costs.
You do have the costs of bandwidth, computing power, and licensing fees. I would imagine those are less than the above.
On top of that, they wouldn't be throwing everything into streaming unless they were making more money there. Even the most retarded of businesses will focus on a more profitable line than a less profitable one.
On top of that, those servers don't run themselves and those infrastructure costs you so quickly dismiss are significant.
You're also making the assumption that aside from the distribution mechanisms, everything else is the same. That's far from the truth. Netflix most likely has to do separate deals with the content owners for DVD and for streaming that likely have vastly different terms.
You're also ignoring the possibility that Netflix views the DVD side of the business as a noose around their neck in negotiating deals for streaming content with the content providers, and the separation is an attempt to free up their hands.
* similar = streaming and disc media - it's the adult space, not mainstream video