What’s the difference between a night out in London and a night out in Hanoi? Around $377, says a recent survey.

Comparing the cost of an evening on the town for two people in popular tourist cities throughout the US and the world, the TripAdvisor TripIndex 2012 found London to be the most expensive destination for travelers, with an after dark sojourn in the Olympic city costing US$518.

Vietnamese capital Hanoi was considered to be the best value international city, with an index cost of $141.

The TripAdvisor TripIndex was based on the combined costs for two of an overnight stay in a four-star hotel, one cocktail per person, a two-course dinner with a bottle of wine, and round-trip taxi transportation (two journeys of two miles). The dates applied to this summer.

According to the index, Europe is the most expensive continent for US travelers, with seven of the world’s priciest cities appearing on the index (London, Oslo, Zurich, Paris, Stockholm, Moscow and Copenhagen), while Asia was deemed the most affordable region, boasting six of the ten cheapest cities (Hanoi, Beijing, Kuala Lumpur, Bangkok, Taipei, Jakarta).

Among American cities, Las Vegas was found to be the least expensive town, costing $263, while unsurprisingly, New York edged Boston as the dearest US city, with a TripIndex tally of $457.

Featuring four of the top ten most affordable cities (Dallas, New Orleans, Atlanta and Orlando), the Southern US ranked as the top region for travelers looking for domestic deals.

The international TripIndex destination list comprises cities from 48 of the 50 countries that receive the largest number of international visitor arrivals (according to data compiled by the UNWTO). The U.S. TripIndex list comprises 15 highly visited US cities, focusing on large and popular tourism markets.

Best Value International Cities:
-Hanoi, Vietnam ($141.12), Beijing, China ($159.05), Bangkok, Thailand ($161.90), Budapest, Hungary ($193.78), Kuala Lumpur, Malaysia ($194.43)

Most Expensive International Cities:
-London, UK ($518.01), Oslo, Norway ($499.91), Zurich, Switzerland ($485.82), Paris, France ($480.76), Stockholm, Sweden ($472.36)

Best Value US Cities:
-Las Vegas ($263.46), Dallas ($283.10), New Orleans ($283.44), Atlanta ($289.80), Orlando ($309.10)

Most Expensive US Cities: