TripAdvisor has introduced TripIndex, which compares the cost of 50 tourism cities worldwide and 15 U.S. hotspots.

TripAdvisor’s TripIndex is based on the combined cost of one night’s accommodation (four-star hotel), a core food item (pizza), an alcoholic drink (dry martini) and a taxi journey in each destination.

Las Vegas is the least-expensive city in the U.S. for domestic travelers, with a total TripIndex cost of $164. Beating 49 rival cities, Bangkok is the best-value global city for U.S. travelers, with its total TripIndex tally of $112. Sofia, Bulgaria, is the most affordable European city for Americans, at $136 and ranking at number five overall on the TripIndex list. Asia emerged as the most affordable continent, claiming four of the top 10 cheapest cities for American travelers.

New York City is the most expensive domestic destination for U.S. travelers, with a total TripIndex cost of $367. Paris’ TripIndex price tag of $429 makes it the costliest city in the world for Americans. Europe was revealed as the most expensive continent for U.S. travelers, with six of the world’s top 10 high-priced cities.

Sofia, Bulgaria, offers the best deal for Americans, with its total TripIndex cost of $136—a third of the price of Paris, the most expensive city on the list. Budapest, Hungary, ($143) is a close second to Sofia in terms of affordability in Europe.

Domestically, the southern cities of Dallas, New Orleans and Atlanta rank among the five least-expensive destinations, with TripIndex costs ranging from $210 to $215. Affordability in the 10 cheapest destinations is most evident in hotel and taxi costs. One night in a four-star hotel in Bangkok is $86, compared to over $300 in six of the 10 most-expensive world destinations. While a five-mile taxi journey costs under $5 in six of the 10 cheapest destinations, the same journey costs around $40 in the likes of Zurich and Tokyo. TripIndex is based on the current exchange rate and applies to travel between June and August 2011 with hotel prices based on the average cost of a four-star hotel found on TripAdvisor, via multiple partner booking sites. For more information, visit www.tripadvisor.com.

City.Mobi

In Europe today, City.Mobi is celebrating the success of its new guide to London.

City.Mobi offers the most comprehensive mobile travel guides available, with over 800 cities in 200 countries listed. Each is developed by the City.Mobi team to combine into a single global travel directory.

However, each city retains its own mobile identity via a dedicated domain. Already on offer are Brussels.Mobi, Paris.Mobi, Sanfrancisco.Mobi and Sydney.Mobi.

London.Mobi is the latest in this illustrious line up, offering click to call functionality – which means no scribbling down telephone numbers.

Most entries are also linked to websites where users can quickly access more detailed information if needed.

Other key features include information on accommodation, restaurants, attractions, entertainment, nightlife, shopping, and transport.

City.Mobi guides include user reviews and traveller utilities such as a translation guide, currency converter, news and local weather guide.