If they know the break-even figure is 13,000, they must know what those 13,000 will be paying.
Collectively, yes, but not individually. I should imagine there will be a whole range of ticket prices, as outlined by Gandolf, above.
Besides, I think the more important point is the cost of the stadium itself. During the delays the costs of raw materials, especially steel have rocketed. Not only that, but we will be building this thing at the same time as the 2012 Olympic sites are being constructed 50 miles up the road. People in the construction industry will be able to name their price and say "take it or leave it."
God knows what the tenders are going to come in at, but I wouldn't be surprised if they will be closer to £100m than £60m, unless the stadium specification has been significantly altered to trim costs.