If they (wholesalers) are willing to dropship an order to a third party at the time it is placed, then it is essentially all small separate transactions. The bulk of the work is the shipping, not receiving the payment. Wholesalers DO tend to only accept unsafe payment methods (WU, MoneyGram, wire transfer), making testing the waters a risky proposition--but you probably knew that.
The simple fact that your order is drop shipped throws "too good to be true" right out the window. Of course it's true.
Yeah, there are a lot of fake wholesalers, and hundreds more who sell inferior or misrepresented product. BUT there are definitely wholesalers out there who sell super reps reliably--the "collectors" take your money then the wholesaler ships you the watch.
It becomes a safe bet as soon as you find the right source; ask your favorite collector.