I think you should remember one thing:
Yaya Han may have had a good experience buying from this person. However, she is one of the better known cosplayers in the western world. Thus, it is likely that she was given preferential treatment above non-name customers.
It's just like the case of a notoriously scummy talent agency that signs everyone and relies on kickback schemes... They have one real working actor with a recognisable face if not name signed, and he is the only one that they treat well and make genuine commission from.
RIP CosRevo, Love Laugh, Sweety Pop, Cocosilver.