This depends on the market. Ideally, an API returns the prices in the currency for the respective market. For example, all Russian OTAs should give us the prices in RUB and sell tickets in RUB and no other currency. Part of the price inaccuracies shown on our site originates from the fact that a currency conversion was applied. By ensuring that the prices returned by an API match the currency of the respective market, conversion errors can be neglected.