Comparing the coffee at the Amex to that in a High Street Coffee shop is nonsense. I tried the coffee at the Amex once and it was by far the worst I've ever had. I wouldn't even claim the free one I got from my Hat-Trick ticket on Sunday.
For me though, one of the main issues is the timing of the announcement. Some people have been taking flasks to games for decades, especially some older people. The club was happy enough to start taking everyone's season ticket money back in April, and everyone quite rightly assumed that the conditions of entry to the ground would be the same as they have always been, given that there was no notification of any change at that time. To now move the goalposts after people have already paid a big chunk of cash is just wrong, especially when the reason given is pretty flimsy.
This is an excellent post IMO. And if the club are going to stiff us with having to buy their crap coffee, then they should contract out the coffee making to a proper coffee house. I'd rather pay £1 extra over high street price for a Costa latte out of a machine (as you might at an airport) than buy their absolute shite.