I guess it depends on if your want second hand or new gear. New is always expensive (obviously )
I think a pfc is around 1.5-2k or something, plus you have tuning costs. Prob looking at the same price for exhaust system if you go a brand name, apexi cat backs are around 1.2k on ebay so i'd assume add an extra 500 or so for the extra turbo back piping and dump pipe.
The nismo kit might be hard to find, i dont think you can buy it new, might be wrond though. If you only like the front bar maybe you'd be better of getting a copy. Yes the rear spoiler is a bit 'over the top'
The rest of the stuff you mentioned is all pretty cheap but I'd budget atleast around 3-4k to do all the mods you wanna do. But second hand will obviously be alot cheaper.
You can get away with not having the pfc as i'm pretty sure the stock ecu is fine for mild boost increases, might be better of geting a intercooler and boost controller as you could buy both those things for the price of the pfc easily, especially if your not after massive power.