Hard to compare the KLM business as NCL with MME as they run totally different planes, different customer types and we have no idea of what the landing fees are.
However on short haul European flights booked with under 2 weeks notice (business people don't generally book far in advance) in my experience are generally twice the price from MME than for NCL. If you book 6 months out, the prices are the same.
I flew into MME twice last week (Tuesday and Sunday evenings) and both flights were virtually full. Friday morning had about 45 people on it (the plane holds about 66 people with the normal configuration). My guess would be that the passenger yield is strong on this route.
The F70 holds less people than a 737 (which is the main plane on the NCL route) but the Fokker needs less crew and probably is fully depreciated by now. Combined with what must be very strong yields, I would imagine the route is pretty strong for KLM. Remember at NCL and LBA they have to compete with BA and others for feed into a hub.