I think you may well have a misunderstanding of the differences between dropshipping and wholesale. Dropshipping will never provide you with a wholesale price. With dropshipping you are purchasing one item at a time, where as with wholesale, you are buying in volume. Of course buying in volume provides you with a lower unit price, something that dropshipping won't do.
Now in regards to setting margins on products, whether dropshipped or wholesale. This relates to your market place, not to the actual product. For example, if you are selling the product on eBay, the most competitive market in the world, then your margin will be dictated by your competition. For example, if you decide that you are just going to throw 30% margin on an item and you have a competitor selling the exact same at 5% margin, then you can guess who is getting the sales.
If for example you are marketing through your own website with no direct competition, then you have more ability to make more margin (within reason of course and given you have the traffic flow required) So your margins on products always directly relate to the market place you are selling in. If any supplier tells you that you can put X amount of margin on, that can only ever be a recommended figure, and in reality, bare very little or absolutely no relevance at all to where you will actually need to set your margin to be competitive in that market place.