He is also one of the most common Pokmon from the Base Set
CGC also makes clear that, in order to determine the approximate value of a card, it will utilize Fair Market Value, which is the price CGC would reasonably expect the card to sell for at auction
Historically the one mana army five drops have been some of the best five drops
The thickness of distribution and ease of buying and selling can directly lead to the strength of the market price
Graded Population Report: Ho-Oh Legend #111 Visualize the distrbution of grades in the chart
The primary upside of this over Howling Mine is obviously that you get to go first, which is kind of like making it a cantrip, but its also worth noting that given the phenomenally clunky nature of spells in Esper Control decks, this might just make a reasonable instant speed threat to play at the end of their turn