Originally Posted by Mr Wrex
The short blocks are 100% identical. The STi has better pistons and substantially improved heads, but they're still not forged. It also has an 11mm oil pump on it.
Most of the prices comes from the other parts you listed, i.e. 6-speed, brembo brakes, slightly bigger TMIC, etc etc.
The heads are pretty much the same with the addition of exhaust AVCS which is essentially useless. I believe they also share the same oil pump now too.