I can't see why they would though. I don't think the RPF has the resources to sell so many units at a loss. I suspect it's probably just barely breaking even on both. The Wifi chipset the Zero W uses costs exactly $5 in quantity according to Digikey; the board layout is slightly different but otherwise the bill of materials is the same so that's the main cost difference. They're probably making some profits off of the accessories like the case or the camera (especially the camera, which is pretty expensive and I expect fairly popular).