Lets get the clear picture first.
Those familiar with tuning and Dyno machine would understand how difficult it is even to get 1 HP increment. And in reality, even 1 or 2 HP increase will be noticable.
I have seen a lot of Dyno sessions for tuning, simply changing Air Filter and Exhaust will rarely give you more that 5HP increment if any at all - unless the previous Air Filter and Exhaust really lousy laa.
So if somebody offers me RM999 for 10% increase of HP, I would ask first if that comes with a guarantee. 10HP from a 100HP motor is quite a bargain and if the claim is valid then it is all worth it. Electronic mods does not require you to do drastic changes to your ride unlike mechanical mods.
Time and time again people would invest huge $$ in bolting on a Turbo or Supercharger kit and at most they are making at around 30 to 50HP for a cost of RM3000 to 7000 (if all of the hidden cost taken into account).
Over the years I have spent no less than RM20,000 (cumulative) on my ride, and yet until today I cant even break the 140WHP barrier - unless I a m willing to invest more on cams, standalone management, race-spec ignition systems and many more.
Power doesn't come cheap, and HP is not everything - for me I personally would love to make bigger improvement on Torque.