Is a glock pistol worth its value?

I bought a glock 21 for $566 including tax and background fee comes up to $640 and I thought it was expensive for a semi polymer/plastic gun even though its a popular pistol I dont know if its worth it or not in the long run i mean i would think its a cheap gun how its manufactured in plastic but i like that its pretty basic. P.s it should pretty good like a gun should and I have a shot a expensive pistol before an sti and glock and sti recoil is pretty much the same?