Prices should be listed with the currency symbol that travellers will encounter, specifically that used locally. The currency symbol should usually be prefixed. Travellers should be able to assume that symbols used for multiple currencies (like $ or £) apply to the local currency. Do not use currency codes like "USD", "EUR", or "GBP" if the symbol is established.
$100 in Detroit, not USD 100, US$100, 100 USD nor 100 dollars
$100 in Vancouver, not CAD 100, CAD$100, 100 CAD nor 100 dollars
In articles where different currencies with similar names might be confused, currency codes might be commonly used in an international context and tourist businesses. In that case, they can also be used on Wikitravel to avoid ambiguity.
When talking about the cost of an item in a country, stick to that country's currency. Do not switch between currencies. Doing so causes confusion and frustration. If you only know the price in dollars or euros, go to a currency conversion site and convert the number. Round off to nearest whole unit.
You can purchase a gift for ₹100. A taxi ride costs $10.
You can purchase a gift for ₹100. A taxi ride costs ₹450.
In some countries such as Cambodia and much of Africa, the local currency is so weak or unstable that any larger prices (like, say, hotel rooms) are quoted and paid for in a foreign currency. If this is the case, follow local convention and list those prices in the foreign currency.
In some countries such as Myanmar, foreign nationals pay a US$ price for some things (hotels, air and train tickets, entrance fees), but in local currency for other things (food, shopping, buses, taxis). In this case, it is best to list the price in the currency that the foreign traveller will use even if it means switching currencies in the body of the page.
Even when the vast majority of expenses will be paid in local currency, if the inflation rate is high enough that information will become outdated in only two or less years, use the equivalent amount in US$. This should be consistent for all articles pertaining to the country.