8k for the kit to be fitted and drive away happy is a fair price, compare it to some of the kits available for other cars and there all in the same price range.
I wouldn't like to guess at the amount of money that's gone into my engine, bigger injectors, smaller pulleys, redesigned fuel system, etc, etc and I'm still not satisfied LOL.
The KB kit running at 400bhp sort of makes the car what it should of been from the start, there's very little difference in fuel consumption (from what I remember
).
Justifying the cost of doing it either way to your other half is hardest part
190 don't do it LOL it's a slippery slope