For overall distance and means of travel comparison, border country travel to either Mexico or Canada is generally cheaper than other countries, assuming the same time span of visit. And between the two, Mexico is less expensive due to the buying power of the dollar south of the border. Both benefit from close proximity to the U.S. therefore reducing travel costs. Trips to Canada tend to be cheaper than overseas due to the country's adjacent location to much of the U.S., making it well within driving distance from many U.S. states.
Countries in Latin American score better on a cost comparison meter than those in Europe or Asia. Much of this again has to do with the economic buying power of the dollar south of the border versus in Europe (dollar -- peso exchange vs. dollar -- euro exchange). Lodging, food and in-country travel historically remain very affordable in Latin and South America versus Western Europe and Asia (which tend to be on par or exceed the higher U.S. cost of living). The cheapest times to travel in Europe and Asia is in the off-season when prices are half their normal levels, but then U.S. tourists typically have to accept cold and wet weather. On the other hand, if an overseas trip is a must, travel to Africa benefits from the same cheaper costs in-country as Latin America when it comes to food and lodging. The air travel tends to the one expensive component for the African continent.
If choosing a European trip, England, Germany and France are far more expensive to travel in since all three use the Euro currency. The dollar is weaker against this monetary value, so buying power is reduced. Italy and Spain on the other hand have historically been far weaker in cost of living, thus trips in both countries remain affordable even if the Euro standard is applied.
Japan, Korea and Hong Kong all represent strong economic zones with significantly developed markets. Thus visiting these areas cost both in the long plane flight and hotel and ground transportation. A better bet and value for the dollar is to go to southeast Asia where all travel prices except air are far cheaper. Thailand is a standout for significant tropical vacation benefits at very affordable costs, especially during the winter months for the Northern Hemisphere.
