I've flown MME-ABZ-MME several times on Eastern, and seen wide variation. Sometimes the aircraft was full, sometimes there were only 2-3 passengers. A colleague of mine once had the aircraft to himself.
In my experience, the Amsterdam flights are normally popular, but as ever you've got to consider not just the load factor, but what people are paying for their tickets. I'd wager that even at 50% loading, Eastern are making money, but I suspect that KL and BD operate on much smaller margins.