It sold for such an astronomical amount is because the test pressing is the only known copy to exist in the world. The Black Album was an album recorded by Prince, but then canceled one week before it’s release. It was given a limited release in 1994, but the original copy is what is most sought after. Almost all of the original copies were destroyed, but a few were kept or found many years later. This one just sold was the only Canadian test pressing every found, though there were some found from US testing plants.