The ENY number for the K4 gets confused by the Ordinance factor. Most think of ENY as how easy it is to get kills, but that's only half the story. The K$ carries no bombs or rockets. So its ENY is lower than a PONY which carries both, and has very long range. You can't close a field with a K4 Raid. Ponies have low ENY because a group can bring 2K worth of bombs across the map, close a field and kill all the fighter that are in the air. K4 can't.
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ENY does not represent the capability of a plane in the attack role. There is an OBJ value for that which determine the number of perks one gets in the attack category. As far as I know if you select "fighter" score, you get no perks even if you drop bombs on structures. K4 cannot select "attack", but the pony can.
Anyway, if perks are the yardstick, then the K4 is clearly valued too high in ENY.
From Lusche's stats thread:

The K4 has a much higher than average effective perk/kill score. It means it kills mostly planes of lower ENY than itself. In addition, it is ranked at the top in total perks earned, but is no where near the top in its frequency of usage in the MA. This means that the ENY value assigned to it fits more a plane which is ranked as "below average" fighter in the combined usage and effectiveness. The K4 is both more effective and not rare in the MA.
If you want to compare to the P51D, the latter got to #4 in total perks even though the perk/kill is extremely low. This just reflect its very high usage in the arena.