Business is booming for New York gold dealers like Isaac Kahan. Here's why everyone is buying and selling gold now.

Visitors to New York City’s famed Flatiron Building may have noticed the landmark’s lesser-known neighbor — a narrow high-rise that would be modest if not for its extravagant gold dome.

One ounce of gold now costs more than $3,200, an inflation-adjusted peak not seen since 1980. For businesses and collectors in New York’s gold industry, that’s changing their finances ...