Aluminum powder coated are cheapest, its not normal plastic that you get in market, UPVC profile is expensive it is extruded from high end German machines.
Both are almost equal in prices. This particular SPARTA Upvc cost 450/- per sqft . Hidalco Aluminum window costs 500+. Upvc costs higher cz of silicon proofing and completely machine made.
I have a question. Yesterday my window has been fixed with upvc sliding mosquito net. I found one vertical side of frame contains rubber knob like thing which can be seen from outside. What is it ?