the few gramms of weight don't weigh up against the price of such a bike.

thats true, and also they are hardly repairable; if you get a crash and carbon frame gets cracked, no repair is possible, all you can do is throw out the expensive frame and make a new investment... but! We're not talking about grams, of course. I won’t see the difference between a 12000 gram bike and a 12050 gram bike... but I will see the difference between a 10-11 kg bike and a 13 kg bike - and this difference is sufficient and, of course, its worth the money they demand for it. Such a solid amount is not 'excessive' in one's budget... that’s why I put it in my post this way: “if a wallet of money will fall on me from the sky ...” ;)