The long beautiful flamenco dresses are called “Batas de Cola” and the art and technique to move them and dance with them requires a specialized training and of course, a “bata de cola” skirt or dress. Students in their 3rd year and up can choose to add bata de cola classes to their regular classes. Bata de cola dresses or skirts are custom made for each dancer and the cost may vary between $300 to $700 or more depending on the cost of the material and the number of ruffles the skirt has, which can vary from generally 3 to 9 or more as seen on the picture below. If you are looking to get one, I recommend you read this article on how to pick a bata de cola.
Below an excerpt from a bata de cola class with Maria Osende in which a part of an “alegrias” choreography is shown.