This is one of many reasons why I am still very uncomfortable with ordering online unless I have no other choice.
I buy quite a lot of things online, and don't usually have bad experiences at all. I always use credit cards for it, so if the deal goes bad, I don't have to pay (though in order for that to happen, one must take the trouble of properly reporting it to the credit card company). But that has not come up as a necessary remedy, and I have been buying things online for quite a few years.
Now, in a case like this, I would stick with authorized dealers, or expect to get a "
grey market" item, and with one from China, it is likely not made for import to the U.S. It might still be a good deal or not, depending on what exactly one gets (one might not get anything at all, but for dealing with that, a good credit card can take care of that problem). But there is definitely greater risk involved with such purchases than buying from an authorized dealer, as Yamaha will likely not give you a warranty at all if you purchase from an unauthorized dealer.