It's not that simple. Too many variables, such as frequency of travel, airline, point of departure, destinations, competition, and so on.
Since airlines began to treat economy pax like cattle, I elected to fly Business Class on long haul leisure travel, but this usually amounts to two, maximum three, roundtrips per annum. Additionally I go for a reasonably good deal and won't pay full whack. I earn the equivalent of an average BA Captain's salary!