Now this is just a theory, but it is safe to say that Sony allotted at least 30k PS4s based on the fact that they were available for 13h and the last 900 sold in less than 30 min. When you consider that the sales per hour were most likely higher earlier in the shipment and factor in the bundles this allotment to Amazon could easily been over 60k, maybe upwards on 80k.
But why so many from one retailer? Well working in logistics myself I think Sony did this in order to get as much product to consumers prior to the 24th. Essentially these console skipped the normal supply chain, if they had taken the normal supply chain they would have missed Cmas. Instead of sending them to warehouses where retailers could then distribute they told Amazon hold many they were allotted and amazon sold them and shipped direct to customers.
This does several things. 1. It's gets the console in the hands of the consumer for Cmas. 2.it transfers the cost of shipping to the consumer increasing the profit margins for Sony (Normally Sony pays the expense of getting commodities to wholesale) 3. It makes them number one on amazon which I could see them bragging about here shortly.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut
