I don't think some of you understand why slim is such a big deal. I worked for a while in operations and a HUGE cost of almost any item is shipping. In the case of something like a PS3 its paid multiple times (once for the truck to the port in china or wherever, once on the ship, once to a Sony US warehouse in a truck, once in yet another truck to a retailer distribution center then once again to the actual individual retail store). If you halve the size of the product+packaging you are literally halving shipping costs. I would bet you anything that shipping the PS3 all those times currently costs 50 dollars (its not light) meaning slimming is at least a 25 dollar cost savings.
Additionally tech has changed so much in the last few years that a slim would possibly cost less by a significant amount. For one thing it would use less materials, for another it would also require less expensive components (smaller tech components can often cost significantly less then continuing to use larger obsolete components). All it all it would go a long way to making the 300 dollar price point viable.
I bet if you added up all the cost reductions going slim would allow Sony would save at least 100 dollars per console. 25 shipping, about 25 on raw materials (plastics and the like) and about 50 on switching the motherboard, processors and other components to smaller more efficient options.
As a bonus, if they went to a significantly smaller processor and GPU (which would be likely) the PS3 would consume FAR less power. It is quite possible for Sony to halve the PS3's power consumption with a redesign.
I think this is both likely and a good idea. I would buy a 2nd PS3 if this was the case.
PSN ID: ChosenOne feel free to add me
