New York City Mayor Zohran Mamdani announced plans to introduce a pied-à-terre tax on second homes of the city's wealthiest individuals, citing billionaire financier Ken Griffin's $238 million penthouse as an example. The tax system undervalues high-end condos and taxes renters less than its market value, leading to a housing crisis. Griffin's 23,000-square-foot penthouse, the most expensive home ever sold in the United States, is valued at only $9.4 million by the city for tax purposes. The city's property tax system requires luxury condos and co-ops to be assessed based on their hypothetical income they would generate if they were rental properties, far underestimating their actual sales value. The New York City comptroller estimates that a tax could generate approximately $500 million annually from an estimated 11,200 second homes with market values above $5 million. However, critics argue that this is not a solution but a substitute for comprehensive property tax reform.