A few comments above regarding predatory pricing, but guarantee this won't be the case as far as EZY is concerned.
EZY's comments about potential BA predatory pricing relate to possibly selling all tickets on a route at a loss, and cross-subsidising from profitable routes (if there is such a thing in BA?)
EZY will never sell a whole flight at these low prices. The first person to book a seat on a flight may get it for £0. The fifth person will probably be paying £15. By the time 20 or 30 people are booked on the flight, tickets will be selling at £50. People turning up last minute, when the flight is almost full, will be paying full whack.
This is a 'loss leader' for marketing purposes and does not constitute predatory pricing as long as they can demonstrate that, overall, the seats are being priced to make a profit.