Bigger a/c = higher fixed costs (eg. landing and nav/airways charges, fuel just to lift the airframe, same crew even if only 50% load, crew hours and crew costs (ie. one crew couldn't do out & back in a day over the Pond), a/c further from base (so bigger probs & costs if it goes u/s), etc.)
So it'll be interesting to see how Jetstar Int'l goes, although I don't think even JI is planning as basic a service as the domestic version.
People will take no food, no recline, no window shade, etc. for a few hours, but perhaps not for much more than the range of a 738 before they start getting a bit bolshie. Even buses stop to let the punters stretch their legs and load up on KFC/Little Chef.