Ian - Prices for these festivals are high enough as it is... charging per space taken by tent would put some right out of the range of many people. As I said above, it's people who've been coming for 20+ years and bring offspring with them who no longer sleep in the same tents but order on the same invoice, it's unsociable staking of territory with windbreaks and the thoughtless (and to my mind, selfish) positioning of gazebos - usually outside tents more than big enough to sit and chat in - who take up the space.

LTS