Can't they just do a draw at a particular date for the people who weren't chosen in the first batch and offer them the chance to buy the rest of the tickets?
They should have just put all of the tickets at the same price. Anyone with any knowledge of theatre would have known that it's obvious that lots of people would enter the ballot to get the cheap seats. It is a fundraising event after all. £15 isn't going to buy RADA very much.
God knows what the bar prices are - £15 for a tin of Coke
Ah, RADA are saying it's now sold out other than Under-25s tickets, so presumably since they asked people if they wanted those they can target their ballot a bit more effectively to get the last few of those sold.