For currency conversions, it is the first currency in a currency pair. For pricing, it is the currency which a tour or activity operator has priced their products and is the main currency accepted for payment.
Operators who offer their tours or activities in various currencies, for the convenience of customers, generally convert the base price using the prevailing foreign exchange rate. At the time of purchase, the price may be quoted in the customer's preferred currency but may be transacted in the operator's base currency. When providing currency conversion in this manner, it is important to inform the customer that the converted price is provided for informational purposes only and may not be the price reflected on credit card statements.
Generally speaking, in order for an operator to receive a payment in a foreign currency, their payment gateway must support the foreign currency. In most cases, accepting foreign currency transactions requires additional bank accounts and incurs additional costs.