No, actually you don't pay any more for the CityHopper sector. In fact you will find that you pay LESS flying CWL-AMS-BOS-AMS-CWL than a poor Dutchman flying Business Class AMS-BOS-AMS. Consequently, your CWL-AMS-CWL sectors are FREE so to speak. Hope that puts a
on your face
Hmm, should have checked before submitting the above, as it seems that what I said is not the case from CWL (it can depend on whether there's competition on the routes concerned). However, checking on KLM's website, I calculated that you are getting your CWL-AMS-CWL sector for about 60% of the unrestricted ECONOMY fare. So, you're still gaining.