Super expensive for that PowerFC without the Commander, but I guess thats what the Takumi Tax brings when its an AE86.
Overpriced? I can pick one up for around $1000-$1100 shipped, so not all that expensive really :)
And yes, bigger turbos and more boost amps up the power, but you also need the ECU to support it.
If I wanted to support an Australian product, I'd buy a Commodore or Falcon (shudders), not a Chaser.