When I was in NYC in 2012 I, too, went to Citi Field for a Mets game. Except it was a much more important game in May against the Phillies.
Loved the field and the city itself, but like you said... would have to make bank in order for me to live there. Too many people and horns for me. Great place for a 4-5 day trip though, undoubtedly.
Shake Shack
is pretty damn good. I went to the one in Madison Square Park, waited 45 minutes for a cheeseburger. It was worth it. Glad you didn't waste time in a line at a World Series game to get a burger, however. Shake Shack is starting to expand pretty rapidly so you'll get a burger from a location sooner than later I am sure.
Glad you had a good experience! Thanks for sharing.