I'd have thought front and rear windscreen were more expensive due to inclusions in them (rear demister, sensors in the front windscreen, etc).
Still not cheap though. And a rotten thing for someone to do, clearly no respect for other people or their property (sadly, lack of basic respect is far too common these days). Not that this sort of thing is new - we had something similar done to a family car back in the 1990s when the family had gone canyoning in the Blue Mountains - every car at the top of the canyon was done in the same fashion, lots of miscellaneous stuff stolen (the damage far outweighed the worth of what was taken).