Believe it or not there is some very well thought out science behind a good balloon envelope storage bag.
Factory balloon bags are horrible. They spend a large amount of time engineering the balloon, basket, burner and instruments and then stick the balloon in a one size fits all type of bag. Generally the bag is oversized because as we all know when a balloon is new it is completely air tight and is hard to get all the air out of it. In fact I believe the coating they spray on the inside of the fabric has some sort of air generating compound in it.