 There are limited to 5,000 pairs, cost about $300. Some sizes were already sold out as of early yesterday evening. And NASA is planning for life after the International Space Station. NASA is contracting with SpaceX to develop a de-orbit vehicle to bring the ISS down gently into the ocean when its lifespan ends in 2030. The vehicle will execute the last week of de-orbit burns. As the ISS goes down, NASA plans to transition to using private companies to operate space stations.