One small fact about banking shows how much detail J.K. Rowling put into the 'Harry Potter' world
J.K. Rowling's magical universe is really elaborate, and one of the more complicated components that most people don't often think about is the economics. There are three different categories of money - knuts, sickles, and galleons - but the exchange rate between them isn't intuitive. And what if you have non-magical money? How are you supposed to buy lacewing flies and broomsticks?
Rowling explained on Twitter that non-wizarding folk could just go to Gringotts, the wizarding bank in London's Diagon Alley. They change muggle money to wizard money.
It makes sense, and Rowling hinted at this before.
In "Harry Potter and the Chamber of Secrets," Hermione Granger - who is a muggle-born witch - meets up with Ron and Harry with her parents. Arthur Weasley, Ron's muggle-obsessed father, notices the Grangers exchanging their muggle cash for wizard-world money at Gringotts.
With so many Euros floating around Britain's economy, Gringotts likely takes those as well. It's an open question of whether the goblins there accept electronic money transfers, like through Venmo or Credit Cards, or have online banking services for the muggles who use it. Magic is known to interfere with electronics in Rowling's world, but the goblins are clever.
In the real-life version of Gringotts Bank at The Wizarding World of Harry Potter theme park in Orlando, muggles can pay real-life money for Gringotts bank notes, which can be used to pay for things around the park, or kept for souveniers. Visitors can also buy souveniers like a Gringotts wallet, chocolate gold coin candy, and Gringotts-themed bank bags. There's also a separate Gringotts Currency Exchange, which works more like a normal currency exchange.
But as far as the wizarding world goes, it's also an open question of what the exchange rate looks like in a post-Brexit world, and how the wizarding economy is faring. "Harry Potter and the Cursed Child," Rowling's sequel to the book series set 20 years later, doesn't really deal with any economic anxiety.