Actually the fares for certain sectors are not that cheap. The cheapest for KL - London - KL (mid week travel off peak season) is RM 1540 (return tax inclusive). Once you include food, luggage and comfort kit, the price becomes RM 1950.

You can get a full service airline like Qatar Airways for about RM 2300 for peak travel with all the extra comforts. So spending an extra RM 350 for comfort on a 12 hr journey i think is worth it.