You do have to weigh up between drop ship suppliers as some will have related charges, such as memberships. You need to see what advantages there are to signing up with one that has such charges over one that has no such charges.
In regards to Wholesalers, it's quite unusual for a genuine Wholesaler to charge any such fees. With a Wholesaler it usually a matter of making application for an account, then you purchase price will, come down to what sort of volume you are buying in.
Of course with Drop Shipping, you usually won't see any great discount on volume purchasing, where as volume discounts is what Wholesale is all about.
I understand it can be frustrating when starting out, however these suppliers are independent of SaleHoo, so we have no control over how they structure their business models.