You have to wonder if this factored into the WWE's decision to award Wrestlemania 28 to Miami, over Toronto. Since the UFC will surely be doing an annual event in the Rogers Centre from now on, perhaps WWE didn't want to compete as the biggest fight event of the spring in Toronto.
"It breaks your heart. It is designed to break your heart. The game begins in the spring, when everything else begins again, and it blossoms in the summer, filling the afternoons and evenings, and then as soon as the chill rains come, it stops and leaves you to face the fall alone." --- Bart Giamatti, on baseball
There is also the small matter that Floyd Mayweather made $60 million in 2009 (according to SI.com, anyway) and that when you make that kind of dough you can work when you want. Nobody in the UFC is in Floyd's (or a lot of the top-earning boxers')