Nebula Dragon
The Nebula Dragon is an EXCLUSIVE pet that was available from the Exclusive Shop. It was released in the Tech Update. It was one of the most expensive Exclusive pets sold, with a price of 5,199 Robux from the store.
The latest Pet Simulator X value list for Nebula Dragon can be found below:

Regular
💎 115,000,000,000 (115b)

Golden
💎 Not Available

Rainbow
💎 Not Available

Dark Matter
💎 Not Available