I too was pleased with the prices. I suspect costs ended up being somewhat comparable on a size to size basis NS4 vs NS3. The new bridle line is more expensive per meter but he groups four attachment points per long bridle line in the "belly" of the kite in the NS4s vs two attachment points grouped per long bridle line for the NS3s.
I'm not in the market personally for larger FB kites but I can certainly ask him. I currently own custom 1.5 and 3.2m NS3s (the latter having been won here on XK!) and depending on how much more I like the 2.5m NS4 than its V3 predecessor I may want V4 models made of those small ones too. In the past Steffen would accept custom orders for those smaller ones so who knows, maybe he still will for larger ones too. I do know that it isn't as straightforward as proportional scaling in his CAD program.
I'll shot him an email and see. Will report back.