The Dressing Room is a new crafting building for the San Monsano area. You can have a max of 3 Dressing Rooms. You can use urgent orders to speed up production.
1st purchase costs 2500 Coins. 2nd will cost 55 GF Bucks and a 3rd will cost 75 GF Bucks. Since the Dressing Room is only used for the Grand Theater Update (right now anyway) I would save bucks and only use 1. Using urgent orders will save you time. (and bucks)