There are DL-coded, 2-segment r/t fares SEA-LED in April found by ITA Matrix from $1,367. Develop some fare search skills, including understanding why your proposed itinerary might not qualify for the lowest published fares. It took me 30 seconds to find that and I suspect LBJ's search MKE-SNN was equally quick.

Unlike, say, a car manufacturer selling a limited variety of products, airlines a selling effectively a great variety of products. It's not just SEA-AMS-LED, it's ~20 N American routes to AMS x 50 onward destinations AMS-XXX -- and that's just the 2-segment routings.