You wont find many people paying for it. If you want that pitch its available in premium economy. Which always fills up after economy. Average Jo wont pay for it, when its available, be a brave man who tried a whole plane like that (might work once a day on a JFK or another frequent route). Airlines work out the yeild per sq m of floor space, in these terms Business normally wins followed by premium the first then econ. Its very route dependant tho.