What is the most expensive ETF in the world?

Could you elaborate on what factors contribute to the pricing of an ETF and specifically, what makes a particular ETF the most expensive in the world? Does it involve its underlying assets, trading volume, or a combination of factors? Is it a recently launched ETF with a high entry price, or has it been around for a while and its price has simply appreciated over time? Are there any specific metrics or benchmarks we can look at to determine if an ETF is considered 'expensive' compared to its peers? Finally, are there any examples of the most expensive ETFs currently available in the market and what are their key characteristics?