From Birds of Paradise to Deathrite Shaman, one-mana accelerants have been bestowed the lovable nickname, "mana dorks." These creatures have displayed a wide range of power level and viability, but Noble Hierarch has always been an irreplaceable piece for decks that play it. Released in Conflux (February 2009), the card first saw play in Mythic Bant during its time in Standard. It then took center stage in Modern for a variety of aggro and midrange decks. Even in Legacy, where Deathrite Shaman has reigned – up until its ban – the Human Druid was and is still used in Infect and Maverick lists.
The format in which Noble Hierarch shines the most is easily Modern. Next to Snapcaster Mage, it is the most played creature in Modern due to its inclusion in Five-Color Humans, Bant Spirits, Blue-Green Infect, Green-White Company, Bant Company, Abzan Midrange, Green-White Death & Taxes, and more.
With Deathrite Shaman in the ban list, Noble Hierarch is now the most powerful Modern-legal mana dork for three reasons: its ability to tap for three colors of mana; its Exalted keyword; and its relevant creature type. Tapping for blue, green, and white allows green-based creature decks to branch out into white or blue with very little opportunity cost. While Birds of Paradise could tap for those colors as well, the Bird carries the risk of being a poor top deck that doesn't really affect the board. The Hierarch, on the other hand, is not only a powerful turn 1 play, but it's also a great card in later stages of the game due to its Exalted keyword, powering attacking creatures. Finally, the creature type "Human" is extremely relevant due to the existence of the Five-Color Humans archetype in the format. The Humans deck synergizes from Human creature types entering the battlefield. When its mana dork fixes its mana, powers up attacks, and works in tandem with other creatures' abilities, it's no wonder the Noble Hierarch cannot be replaced.
A copy of Noble Hierarch was only for 10,00 € during the infancy of Modern and anyone who didn't hoard the card during that time might be kicking him- or herself right now. Currently, the card fetches a price of around 25,00 € (Near Mint), although it has experienced its share of highs and lows during its nine-year existence.
The card's price peaked during Khans of Tarkir (September 2014) due to the popularity of Blue-Green Infect, but Noble Hierarch's reprinting as a Rare in Modern Masters 2015 then again in Ultimate Masters (December 2018) saw its price plummet. Since then, the card has had only a few intermittent dips. As a Mythic, however, it can still cost you around 85,00 € (Near Mint).
Combined with the creature's importance in Modern and its irreplaceability, Noble Hierarch will maintain its price tag until more reprints come our way. Even then, don't expect its price to permanently drop to single digits.