270rwkw "on the cheap" is:
Turbo + install + dump/front pipe + cooler piping - $2000
Injectors 2nd hand - $400
ECU 2nd hand + Tune + AFM - $1500
Clutch - $1000
Cooler kit - $500
You are @ 5.5k just before you start, and using 2nd hand parts and other parts that are not exactly the pinnacle of performance.
There are other factors like coil packs, other sensor issues, labour/drama/trouble shooting etc.
Also you make no mention of suspension or brakes with even just better rotors/fluid etc. Thats another 3k.
Realistically, to have it safe and reliable its a 8-10k adventure.
So its pretty simple. If you can't afford it, then don't bother.