Cost of living is complicated and lifestyle-dependent, and living in the city core vs. the suburbs makes a huge difference in most places. According to Forbes and The Economist, Singapore is #1. San Francisco may have laughably-high rents, but the cost of consumer goods, food, and many other things is far cheaper in San Francisco than in Singapore, for example, and it heavily skews the results.
Singapore is a "top 10" city by any metric and that was the main point.
