"During nights lights are OFF which makes a kind of a black hole effect on flare."
I'd suggest to take the controllers on a cockpit ride. Could be an eye opener.
What's the cost of an aircraft running off the runway, or just a diversion? The "actual" cost of leaving the runway lights "on" are really insignificant, but every 2 or 3 years an enterprising "paper-pusher" will get the "saving" idea of the year. (i.e. NOT to use the runway lights. Happens here in the "1'st world" (?)
too!)