Read actual info here: https://www.paypal.com/en/cgi-bin/webscr?cmd=p/sell/mc/mc_wa-outside
If the currency is omitted of the list, the default currency will be U.S. Dollars - so be care with adding currencies into woocommerce store as acceptable by PayPal - on PayPal checkout page if currency is not acceptable amount will be the same but in USD!!
Customer decided to activate PayPal gate for Korean Won KRW by the next script:
$paypal_currencies = 'KRW';
But it is a wrong way to making acceptable payments in the currency you want as it is NOT in the PayPal list of acceptable currencies!! Do not do it to avoid confusing with payments!