How was your experience?
High Tea in the Great Hall is a character event - you are paying for the experience of interacting with some of the Harry Potter Characters, more than for the tea. Great photo ops, and the actors/characters were very friendly and that made this worthwhile. It is very expensive-- the tea was lukewarm, the food was OK, and though this is priced like a true high tea the money is for the experience and not food and drink. If you go with that expectation, and get a great deal (like Goldstar), you will leave happy.