Simple answer to that one Gas, electricity, food water etc have all gone up by way more than City's season ticket prices.
I would say the average wage in Brentford is well above the average wage in Manchester and almost certainly the average wage in Southampton and Leicester is below that of Manchester (just googled it - Manchester £37k, Leicester and Southampton £32k, London £46k). The costs of watching football have become significantly below the costs of watching other entertainment like music and theatre (O2 tickets go up to £240 - which is ridiculous). On top of that the below inflation increases in City season tickets have not reduced the demand for the tickets with most games still pretty much selling out, hence the current expansions.
As i said there are 16 premier league clubs with higher season ticket prices that City so I'd say they are doing better for the fans than all but 3 other ones whilst at the same time providing better performance and entertainment than any of the others.
One thing to note on this story by the way is it is about City's BRAND being the most valuable. It is not about City making loads more money it is about the brand. Though yes with the increase in brand exposure there is the potential of making more future revenue.
There is nothing in my posts about not being bothered about the cost but I'm afraid it is just the reality of the world.