Just to offer an alternative opinion.
You are watching the Champions League finalists and the current top 2 in the Prem League. You're also watching a team coached by the finest in Europe with players doing amazing things. This game will be watched by millions globally that would give their right arm to be there.... you can to, for only £63.
Apart from the Rags and the Dippers or PSG in the CL, games don't come much bigger than that and tickets will be in short supply, so why not charge that amount for a big game?
It's when City still charge the same against the smaller clubs, or shit kick off times or just before Xmas, etc that I have a problem with.