As Rohan mentioned I have a DrDrift chip as well. Bang for buck I swear by it. Sure its not a full motec, but I mean its a street car.
But yeah, mine was just Sams off the shelf for basic modded RB20s (ie cooler, bit of boost filter etc) so all we did was plug it in, wack it on the dyno to check it all was running fine, which it was. So it was the cost of the chip, and the cost of a dyno run. My afrs are a perfect 12, so much so you can almost run a ruler along the afr line. Power was up about 15-20kw atw before the chip. Way way more mid range. And most importantly it did all of that AND I get more kms per tank of fuel, approx 50kms to every tank to be exact. Add to that no boost or speed cut, and the rev limiter moved.
So if you have a basic modded RB20 that might be the way. Get the chip up by post (REALLY easy to install), put it on the dyno then go from there. Mine didnt need any extra tuning, neither might yours. As everyone else has said tho. Talk to Sam.
But for me about 2 years ago it cost like $450 or so with the dyno time.