The average designer One Shoulder Prom Dresses costs between one and two thousand dollars, depending on the designer, of course. Another important consideration is the Plus Size Prom Dresses. Many brides-to-be like to shine on their special day, and this may require special additions that must be hand-applied to the dress. Crystals, sequins and even pearls may be added to a designer Short Prom Dresses. As you might expect, this will also add a few hundred dollars to the final bill.