According to the DWS Housing Affordability Report 2025 (pdf) - page 4 on the linked pdf contains a diagram comparing global cities - lists London among the least affordable cities citing. Within Europe, only Lisbon is less affordable.

In a nutshell:

• Salt Lake City and Austin maintain first and second place as the most affordable locations, while Brisbane, Melbourne and Sydney climb the ranks compared to last year, completing the top five.
• US cities continue to be some of the most affordable globally, due to high income levels and often fewer supply barriers. Five US cities appear in the top 10, including San Francisco. However, New York and Miami remain notable outliers.
• Australian cities also score well, although Indian and Chinese cities pull down the APAC average.
• Europe sits squarely in the middle, although with notable outliers including a surprisingly affordable Munich, and the increasingly expensive home of digital nomads, Lisbon.
• Despite low affordability, global cities like London, Paris, New York, Berlin and Tokyo continue to attract people through their culture, career opportunities, energy and lifestyle – making high rents a price many still appear willing to pay