Specifically regarding the EJ207 shortblock having cast, not forged pistons:
MY03 EJ207 STi Piston Set -- $1022
This latest STi piston is a departure from previous years in that it is a cast aluminum design. However, we believe this to be a special hypereutectic material and STi claims a 120% increase in strength over their previous forged pistons. The high silicon content of the aluminum also has the benefit of providing exceptional scuff resistance and reduced thermal expansion which allows for the use of tighter clearances. Compression 8.0:1.
I also respectfully question the comments regarding the reasons for the price of the US vs. International (UK?). STI. The UK STI makes 265 hp and doesn't even have DCCD standard. Why would it be more expensive to make? It's notoriously difficult to compare msrp's in different countries.
You are just quoting the same source (North American component reseller). - My previous comments stand.
We engineer and supply components all over the planet. I was not quoting U.K. pricing specifically; after all, we are in Australia.
With regard to the short engine cost, the international spec STIís use a low volume, hand built, genuine STI short. (Rods, pistons, bearings, crank, block, all are unique). The US spec. car uses a high volume, assembly line, short engine from the Forester.
The difference in cost in parts and more particularly labour, resulting from these two approaches should be obvious.
All the best,