Shoebox want $25 min order to ship anything OS. Postage was at least another 10 IIRC. So for 1 brush I didn't bother. I'd jump in and split postage if that makes it worthwhile.
Conns would be a better bet for one offs though.
Conns want $5.61 for shipping two brushes. Shoebox doesn't even come close. The brushes are also nearly 50% more.