Wrong calculations. I've checked several times while going to isbd and in local too. Let me tell u exact calculations. Calculations are with respect to going from peshawar to pindi thru motorway
If i fill Rs. 400 CNG, i have to refill after 173 km=2.31Rs. per km
I have to put Rs. 1000 petrol to cover the same distance=5.78 Rs. per km
More than 50% difference. Now after returning back, that Rs. 400 CNG becomes Rs. 800 and Rs. 1000 petrol become Rs. 2000. Isn't it better to save Rs. 1200/- in just 5 hours?
No CNG kit is for Rs. 60000/- or Rs. 75000/-. Correct me if im wrong. CNG kit installation in corolla/civic is for Rs. 48000/- maximum. (Landi Renzo Kit, EFi electronic conversion button, 55KG cylinder, Emulator/advancer)
Its environment friendly, remember only 15% of population in the world is able to afford new cars having zero emission technology. Its no doubt cost effective.
About lowering performance, if your equipments are original and mechanic is good. There will be negligible performance difference.
About spoiling engine. Research has proved that there is no harm to the engine and that is why, Mercs, LCs and civic are also having versions with company fitted CNG. Let small cars like suzuki, hyundai aside.
And yes, i agree with @tevi0n. Let's take that into another aspect. MashAllah u may belong to a well off family that can afford petrol but in pakistan, being a 3rd world country, not everyone here is like u. May Allah bless u with more n more