RingwaySam, I think that what you forget is that not all seats will sell at that price, maybe only the first 10 or so. The price will then increase incrementally and the majority will sell at much higher fares. They call it yield management or something like that. What is being said here is that a charter wouldn't be viable if all seats were sold at the price indicated.
As an example if I now wish to book EASYJET LPL-FAO-LPL, out 18/AUG with a return the next day, the cheapest I'll pay is over 170 quid.