Dress making satin? how much and where from?

My dress - maker needs around 25 meters of burgandy satin to make my dress, my partners suit and my flower girl dresses. She said either I can buy the material or she will. what I need to know is what is the minimum quality the satin needs to be, how much per roll or metre to expect it to cost and where is the best place to purchase it from? Also if I go to a fabric store exactly what should I be asking for?