Direct answer: Based on recent cost-of-living and housing reports, San Francisco, New York City, and San Jose consistently rank as the most expensive U.S. cities to live in, with San Jose often at or near the top for housing costs, and New York City and San Francisco leading in overall cost of living metrics. Context and nuance:

• Housing costs are the dominant driver of overall expense in many headlines. In several 2024–2025 analyses, San Jose and San Francisco top median home price lists, reflecting Silicon Valley dynamics, while New York City and Los Angeles frequently appear at the upper end of cost-of-living rankings that include rents, groceries, utilities, and transportation.
• Different organizations measure “most expensive” in slightly different ways. Some focus on housing prices (medians, price per square foot), others on composite cost-of-living indices (rent, groceries, utilities, transportation, and taxes). As a result, the exact order can vary by the methodology used.
• For prospective moves, consider:
  • If housing affordability is the primary concern, San Jose and San Francisco typically show the highest median home prices, with San Jose often leading in 2025 housing-cost reports.
  • If overall day-to-day cost matters more (rent, groceries, utilities), New York City and San Francisco frequently rank at the top in many composite indices.
  • Other cities like Los Angeles, Boston, and Seattle frequently appear in the top tier depending on the measure used.

If you want, I can tailor a concise ranking based on a specific metric (e.g., housing prices, rent, or a composite cost-of-living index) and include recent sources.