I believe that longhaul economy fares with "legacy" carriers are, generally speaking, about as low as they can be - effectively, passengers in other cabins are "subsidising" restrictive fares in economy. The only reason why an airline like BA, for example, is able to offer such low promotional fares in economy is the fact that First, Club and, to a lesser extent, World Traveller Plus fares are so high in comparison. Not even MOL could, I think, match these economy fares and make money, though not being an aviation economist I could be wrong....