I believe, I saw the same for $10 before, but couldn't find that thread.
Anyway, Gearbest (w/ very poor security) has Original Xiaomi Smart Home Aqara Human Body Sensor for $10.99 + FS.
I received an email with this price. And the product page says that is the price of $10.99 is "email only price". Not sure what means, I would simply say YMMV.
I don't own this product, but from review, it looks like this works well with smartthings w/o any custom DH.
I ordered 1 for myself, using paypal.
Link from email: http://e3ai.gearbest.com/r/link/3...3979116II5