New xps 13 developer edition 8gb/256gb costs 200$ more than the windows one

I was looking into buying the Dell XPS13 developer edition and as one can see: http://www.dell.com/us/business/p/xps-13-linux/pd?ref=PD_OC going from 128gb ssd to 256gb costs a 400$(949->1349) premium, which I found very surprising. So I checked the windows model as well: http://www.dell.com/us/business/p/xps-13-9343-laptop/pd?ref=PD_OC only 1149$, 200$ cheaper + windows license!