Apples and Oranges. The MEN has a maximum capacity of 23,000, and everyone who buys a ticket knows they will get at least a semi-decent view. Wembley seats near enough 100,000 with seats on the pitch, and most of those are so far away from the centre of the field that people will, quite rightly, think twice about it. Bear in mind that the centre circle is 20 yards (60 feet) across, so the ring would only take up just over a third of it -- and Wembley has a big-arsed FIFA-grade pitch to start with, not like some city football grounds. On top of that, Wembley has no massive screen like Cowboys stadium (it's got screens, but they're not the same scale or position), so if you were seated in the corner of the top tier, you'd see pretty much nothing. When Calzaghe was at the height of his popularity, they 'only' sold 50,000-odd at the 72,000 capacity Millennium stadium, and that's even more intimate than Wembley is. As someone else said, they could probably do 50-60K, but not fill the whole arena.