The cost of the Olympics in Beijing was approximately $42 billion. Much of the cost is in the building of the Olympic Village so the total cost would be less in a country where labor is less expensive.
In today's world hosting the Olympics can cost a city BILLIONS of dollars. Costs come from building structures that fit the specific needs to the security needed to keep all those attending the Olympics safe. Increasingly advertising and promotions can add considerable cost. Each must be done no only in the city hosting the games but around the world.