Ummmm.....maybe that’s because the Sportster only went for 1/3 of what the big twin went for in the first place? For what it’s worth, I’ve never sold a Harley that I didn’t make money on. Well, I did put over 200,000 miles on one, so if you can’t count the cost of the 2nd engine, I might have lost money.
I let people use the arguments on me of Harleys are too high, they don't perform well, they aren't reliable, etc., but the simple fact is buying a motorcycle is not a rational act, it's an act of passion. If you want a Harley, get what you want as long as you can afford it. Oh, and take the riding class.