For a city situated in what used to be the United States of America, having a major currency based on the European Euro may seem odd to players of Cyberpunk 2077. The Eurodollar is the primary currency of Night City in Cyberpunk 2077, and despite it being a core part of the experience, it is never given a proper explanation in-game. To find out the origins of this mysterious currency, one has to look to Cyberpunk 2077's tabletop RPG roots.
Cyberpunk 2077 is set in the Cyberpunk setting created by Mike Pondsmith, and takes many of its characters, settings, and themes from the tabletop RPG. Night City, Johnny Silverhand (who existed before Keanu Reaves' portrayal), and the Eurodollar all stem from Pondsmith's RPG world. For fans of Cyberpunk 2013, Cyberpunk 2020, or Cyberpunk RED, the streets of Night City in Cyberpunk 2077 will feel like a fully realized version of their tabletop world.
Cyberpunk 2077's Eurodollar (colloquially known as eddies), or Eurobuck as it is known in Cyberpunk RED, is the world of Cyberpunk's foremost currency due to the stability of the economy of its native European Union. The EU economy is so stable that its currency became the norm the world over, much like the American Dollar before the in-universe collapse and corporate wars. Thus, even though there are competing currencies in the world, the Eurodollar reigns as the standard to which other currency is measured, and is therefore the most widely used.
The Eurodollar Survives In A Tumultuous Cyberpunk Economy
Cyberpunk 2077's economies rally and crash overnight, governments can fall at the drop of a hat as with Cyberpunk 2077's NUSA looking like a dystopian version of modern America, and money can go from worthwhile to worthless in even less time. With everything in the world in the process of becoming something else, a theme reflected in Cyberpunk's transhumanist denizens, it makes sense that global corporations and citizens look for some stability in their currency. According to the handbook for the Tabletop RPG Cyberpunk RED, "Since the European Union is one of the most stable economies on the planet [...] the eurobuck (or eb for short) become the "gold standard" to which all other currencies are currently pegged".
That being said, Night City is situated on North America's West Coast between the two states now known as Northern California and Southern California, far from the influence of the European Union. Combined with the heavy influence of Cyberpunk 2077's Arasaka Corporation in Night City, it is a puzzle that Japan's New Yen currency isn't used as standard in Night City instead of the Eurodollar. From the lack of New Yen in Cyberpunk 2077's economy, it can be inferred that the currency simply isn't as strong as the Eurodollar in terms of buying power, and the de facto leaders of Night City ostensibly recognize the Eurodollar as the official currency due to this.
The Eurodollar is a Cyberpunk 2077 player's best bet when it comes to a stable, predictable currency to use in the various markets of Night City. It is also the only recognized currency currently in the game. With the buying power afforded to it by the most stable economy in 2077, V should have no trouble purchasing whatever they need in Night City's variety of shops.