The more I think about this the more farcical it feels. Sony just want some mind share when Oculus and Vive are launching. They're a long way off but don't want the public to see it that way. Sony have no clue how many they can produce for launch. This token batch of pre-orders is nothing more than a cheap attempt to grab some headlines and stop Sony being forgotten.
Or like any business, want to gauge the interest of their consumers about the new product that they are going to release in 6 months time, find out how many people are willing to pre-order it and logically get a forecasted number of units they actually need to manufacture.
Or do you feel that should make 10 million straight up and hope there are 10million people that want to buy into it?