I've only placed one order with them, timing chain kit , neutral switch, master cylinder and caliper kits and a few other odds and ends, all light parts and I think the shipping was around $10 to Phoenix, this was over 4 years ago also .
If they are heavy parts, the shipping costs will get quite costly .
I don't think there are any sources in the US where you can get discounted prices on BMW parts .
You'll have to do some searching online yourself and see , Max BMW, if I'm not mistaken is in NH, from what I've heard, a very airhead friendly dealer .