From 1997 to 2007, Wizards of the Coast invited pro players to the Magic Invitational Tournament. The winner of the tournament could submit a design for a card and the printed card – with or without changes from Wizards R&D – would bear a likeness to the player in its art. These Invitational cards ended up being very powerful, as was the case with Meddling Mage, Dark Confidant, and Ranger of Eos. So, when Tiago Chan won the very last Invitational in 2007, the Magic world waited with bated breath for the printing of his card. It wasn't until four years later, when Innistrad was released on September 2011, when the world was finally introduced to Snapcaster Mage. It was worth the wait, however, as Snapcaster Mage would become one of the most powerful creatures ever printed in the history of Magic: The Gathering.
Here's a good rule of thumb about Snapcaster Mage's place in a format: If Snapcaster Mage is a legal card, then it's one of the best in that format.
Snapcaster Mage sees heavy play in Modern, Legacy, Vintage, and in any blue deck that relies on Instants or Sorceries. The reason why the card fits so seamlessly in a wide range of decks and formats is due to its ability to give flashback to Instants and Sorceries in your graveyard. A tempo deck in Modern can close out a game by casting Lightning Bolt, playing Snapcaster Mage at the end of the opponent's turn, flashing back the Bolt, then dealing the last two points of damage via combat. In Grixis Control in Legacy, chain Kolaghan's Commands and Snapcaster Mages to make your opponent discard, return Snapcaster, then flashback the Command. In Blue-White Mentor lists in Vintage, Snapcaster Mage double-dips some of Magic's most powerful spells, Ancestral Recall and Treasure Cruise. Whatever the Instant or Sorcery, having the blue Human Wizard in your deck makes spells twice as good as they would be without.
Although Snapcaster Mage debuted with a price tag of around 20,00 €, the card has seen a sharp rise in value in the seven years since then. It now hovers around 50,00 € (Near Mint) even with a reprint as a RPTQ promo and a Mythic Rare in Modern Masters 2017 and Ultimate Masters (December 2018).
Due to its popularity, Snapcaster Mage has been the center of speculation whenever a reprint set is announced. But there's no guess as to when – or if – Tiago Chan's card will see another reprint that will bring down its price anytime soon. In any case, one thing is for sure: It's unlikely that a strict upgrade of Snapcaster Mage will ever be printed.