I think it was scaled back compared to the 1953 coronation - far fewer guests in the Abbey partly to H and S concerns which weren't a consideration then. The cost is mainly due to wages for personnel involved, isn't it?
I'd be interested to know how much money will have been recouped from foreign TV rights. I read somewhere that it was already covered, but I don't know how to find confirmation of that.
My view on this is that pageantry like this is something we do better than anyone else. The show that gets put on is just incredible every time and London always looks amazing. Why don't we stop stressing about the cost (and other matters - see below) and just think of it as something we're good at, a quality product which we export and earn money and prestige from? We should chill out about it.
I'm not much of a one for principles - I'm a pragmatist. Frankly if people enjoy it and the net result is income for the country and prestige abroad, then go for it. We shouldn't get so het up about it. Isn't the cost of the monarchy annually something like £2.95? (But please correct me here.) Would people really rather have that - not quite enough for a flat white - than all the pretty horses, handsome soldiers and gold carriages? Some people would, but I think they're mistaken!