Moscow has topped the league of most expensive cities for expatriates to live in for the third year running.The research by human resources firm Mercer took account of expenses such as rent, eating out and petrol.Moscow has particularly expensive coffee, with a cup in a cafe costing $10.40 (£5.19) including service.Tokyo climbed two spots into second place in the survey, followed by London, which dropped one place into third and Oslo, which came fourth.The survey compared the cost of 200 items in 143 cities. The three cheapest cities were Karachi in Pakistan, Quito in Ecuador and Asuncion in Paraguay.Asuncion was the cheapest city for the sixth year running.