I have been working on WRx's for 3 year's, And a Certified Nissan tech, But money sucked so now im in sale's.
I just got done helping a friend with his 02 wrx with knock. We did his R&R for 1500 complete and up and running. That is 600 for motor and 900 for me.
But On the forums you can pick up a ej20 for a few hundred. Now on nasioc theres one from 400 (Just the short block). 100 for head gaskets and throw your heads on there. and your set. unless you have to pay for labor.
Or go with the STI short block and your heads (Im running a non sti 2.5 with ported and polished heads in my wrx This set-up on other cars have seen above 500 awhp so its a nice and cheap set-up)
$$$$$$ Is determined on what you want.