Some cosplayers make their own costumes. Some buy them. The price range for costumes can go from affordable to totally not.
The costume you are looking at costs ¥98,650 (US$1,172). It’s the duds for “Purple Heart”, the goddess version of Neptune, the main character of role-playing game Neptune.
In the costume, that’s Rie Tanaka, who voices Neptune and Purple Heart. She also not only has voice credits in Phantasy Star Portable and Shin Megami Tensei: Portable 3, but also her own trading cards.