You can search your library for any dragon at instant speed, reveal it, and put it into your hand, giving you the perfect threat or answer depending on the situation
Not to mention that SR Supporters from those sets are also technically SR (full art)
At the beginning of each end step, if a card left your graveyard this turn, Gau deals damage equal to its power to each opponent
Second, configurations change between sets and special products (elite trainer boxes, tins, and collections all differ)
Also, its Spark move only requires two Lightning Energy, it deals 40 damage, and will inflict 20 extra damage to one of your opponents Benched Pokmon
Its price reflects steady tournament demand rather than collector hype, which makes it one of the more durable holds here