Ummm I dont know where you're looking or whether the prices you mention are in Singapore $, but:
Civ V Beyond Earth is $49.99, not $89.99 - This after you could get ALL the CIV5 games on sale for $29.99 a week ago. Has DBC's price dropped in the slightest or seen a week special like many of those games? no
Metro Redux is a 2 game Bundle for $49.89
The Witcher 3 - $53.99 and this game will only be released in Feb 2015
Most of the elevated prices you mentioned are for Gold or Special Editions and many of those prices are for games not even released yet...so thats not even a fair comparison. The Special Edition of DBC is available here in South Africa to the equivalent US$70.00, so there's that.
Perhaps its just been too long since I played PC games, but $50 is what I would expect to pay for a console game which is a couple of months old, not a PC game.