We should include a disclaimer here - James Goldstein and the much, much younger Amalie Wichmann have always insisted that they're not married, because Goldstein doesn't believe in marriage. They're always together, though, and so it would be foolish not to believe they're a couple.
Goldstein is a somewhat eccentric character, known for his outlandish outfits and his love of NBA. Maybe it's his unique sense of style that drew Danish model Wichmann toward him. The fact he's a billionaire might just be a bonus.