Great post mate, it's a very good point regarding inflation.
The £50m figure is what I have always seen quoted as the price of the South Stand rebuild. Maybe this is inaccurate, maybe the additional cost was due to the unique roof we have. I'm not sure.
But I agree with you, looking at the basic supply and demand argument, there isn't really a viable case to go ahead with an expansion right now. Perhaps in one or two years time there will be a compelling case for expansion? Who knows, I certainly hope so.
I'm not sure how much an additional 6k on our capacity will affect commercial deals. Personally, I don't think it will have too much of an impact, if any at all.
Of course it would be great as a fan to have 60k plus blues there every week. An extra 6k cheaper seats to bring back some of our core fans who can't currently afford it would be brilliant and hopefully help with atmosphere. But being realistic, the only way that can happen financially is if prices increase elsewhere and there is more corporate seats. I just don't think the demand is there for corporate tickets yet at The Etihad.