I got mine done for mid $900... $960 maybe? Male it a round $1000 to be safe. That was fitted and tuned. Runs like a dream, smoother all round and slightly more fuel efficient as well
The Nistune solution has several advantages over other systems as it maintains several factory options such as cold starts, R+R if something goes wrong etc that the aftermarket ECU's can't compete with. Nissan spent millions developing and tuning their cars, no 3rd party will ever get the basic stuff as right as they did. that's part of te reason why I went with it.