I am just pricing a trip to Copenhagen in the middle of next month and the options so far (in Y) are:
SAS - GBP 108
British Airways - 109
easyJet - GBP 127
Ryanair - GBP 130 (to MMX/Malmo)
I hope that this data will put into perspective that the loco airlines tend only to be competitive with the majors well in advance.
Now, as it happens, it suits me to fly from STN on this occasion and I'll probably choose easy, but if you factor travel from central London, the Stansted express is several times more expensive than the tube to Heathrow. So for many travellers, they could pay 30% more to travel low cost and we aren't talking about turning up on the day - this is 3 weeks in advance.
So BMIBaby, the data simply does not support your argument. Flying is a zero sum game, as WHBM says and someone always pays more so that someone can pay less.
In the major carriers, the F, J & W pax (& full fare Y) cross subsidise the low cost Y seats (and receive better service levels, except full fare Y), but what do you get back if you pay top end with a loco?
Short answer - nothing.
So, in order to convince me that loco carriers are truly loco, I would like to see them price the cabin at a simple pricepoint (like Laker used to do with Skytrain) and then we will see what that price is.