It doesn't look like the choice was an economic one, unless they completely missed the mark with their projection of GDDR5 cost. They were targeting 4GB at some point ($14 difference between DDR3 and GDDR5) and ended up with 8GB ($28 difference).
All else being equal, the cost of die area for the ESRAM is practically compensating that difference (something like 1/4 of a $100 chip?), and it would have been a more expensive proposition, comparatively, had they went with the original plan of 4GB. In short, their 4GB solution of DDR3+ESRAM would have been more expensive than GDDR5 and no ESRAM.
14 USD over a million consoles would be 14 million USD. 28 USD would be 28 million USD. For MS that is a drop in the bucket. For many other companies, Sony included, that could determine whether they'll be in the red or in the black. With PS4 shipping over 10 million consoles in it's first year, that's 280 million USD.
How relevant is that? Sony minus their financial services had a net loss of 117.8 million USD for 2013. A 280 million USD swing would theoretically have swung it into the black.
Now, that isn't to say the investment was bad. It lead to a good performing machine that is also performing well in the marketplace. As long as software and hardware attach rate (where the profit is actually at) is good, then their decision should be an overall profitable one. Especially as time goes on and they, presumably, extend their market lead over the competition.
But the point here is that while it's easy as a lay person to look at 14 USD and 28 USD as being so low as to be meaningless, when it comes to the financial balance sheet of a corporation that plans on selling 10's of millions of units, it represents a relatively huge investment.
It's why there has to be a large justification for inclusion of a component that costs even 1 USD or even a fraction of a USD. Because that 1 USD part could be the difference between a profitable company and an unprofitable company. For example, at 1 USD, 10 million PS4s would be 10 million USD. Sony's top executives are going to return their yearly bonus for 2014 in an attempt to help the company become profitable. The total worth of their bonuses? 9.8 million USD.
If Sony again (minus their financial division) has a loss this year (quite likely with current financial news coming out of the company), it's entirely possible their board of directors could look at the cost incurred by the inclusion of GDDR5 as a point where they could have been profitable if they had gone with a cheaper memory solution. Of course, that would be short sighted as the design of the PS4 requires GDDR5 to have good performance.
TLDR:
So, in short, yes. It is quite likely that DDR3 was a cost conscious decision. Especially going forward where after a few years they may have been the only consumer of GDDR5 in the marketplace versus DDR3 which will still have many corporate consumers. IE - the cost differential between DDR3 and GDDR5 should widen over the next 5-10 years assuming newer graphics memory solutions come to market.
Regards,
SB
. It was first used in Uncharted. This technique was really important for PS3 as the SPU local memory was small. Tiled lighting allowed processing the lighting inside the SPU local memory. This technique was really popular in PS3 games. I think we were the first ones to use this method on Xbox 360 (Trials HD, 2009). Black Rock used it also on their Xbox 360 game Split/Second (2010). Battlefield 3 was the first AAA game to use compute shader based tiled lighting method on PC (if I remember correctly).
