Initially it will be, only difference being you will hit your brick wall later. But depending how far you go, you still need forged internals, bigger turbo, fuel system etc etc it goes on. So in the end they are both roughly the same costs. There both different and ultimately it depends how u want the car to deliver its power, the noise to 8k is addictive tho! Pros and cons to both really, but neither are disappointing.
Don't ok where your getting 4k from with someone else doing it. Mine would be 5.5k for 260/70 drive in drive out. K tecs is 240ish but I suspect they are using a smaller charger than mine. Charger alone is £1700 ish, so if u fit and install the unit and ecu yourself all u will need is to get it mapped. That's the unknown cost as no one has done it.