Low Cost refers to the lean, mean business model and has no relation at all to the fares charged! I still can't believe how few people seem to have grasped the concept that, apart from the few lucky ones who grab the early booking cheap fares, you can actually pay a heck of a lot more with EZY and RYR than with the "heritage" airlines! ..........and if they don't actually charge a higher fare, they will claw back the differential and more in other ways.
Bear in mind, the "heritage" carriers already had low fares for early bookers (remember APEX and SuperPex etc?) - okay, maybe not the daft 1p gimmicks that swamp RYR's web-site and cause a systems failure, but BA and British Midland both used to have £13 return fares on our UK Domestic services to let Grandma come down to see the kids once in a while! The low fares weren't advertised, we just discreetly got on with the job of always charging the lowest fare applicable for the journey type, as per corporate policy!
My next door neighbour, a contracted aircraft engineer, had to fly to Madrid in a tearing hurry. He had the choice of being "waitlisted" as a Club Europe passenger with British Airways at £572 (giving Lounge Access, Full Catering etc) or confirmed with EZY at £680 (a fare of £108 higher than the highest " Full Service" fare.)
Because the job was so urgent, he reluctantly took the EZY option who then proceeded to sting him for excess baggage charges!