I'm not going to fall out with anyone (will be my one and only comment), but ignoring the football we watch for a minute, I think the rise is pretty reasonable, and the biggest reason for that, is that City are a business.
Businesses (and individuals, as many are pointing out) are having to take on often huge price increases, so why should City (just like Tesco, or your local pub/restaurant) not pass it on the same ?
We all know that the costs of running any business over the last 12 months has gone up a lot more than the 5% (ish) City are asking. I would imagine that costs of contractors (staff and supplies) has gone up very significantly, not to mention energy price rises for both the club, and it's contractors.