WooCommerce Checkout Add-Ons (by WooCommerce)

function wc_checkout_add_ons_woocs_currency_support($cost) {
    return apply_filters('woocs_exchange_value', $cost);
}

add_filter('wc_checkout_add_ons_add_on_option_cost', 'wc_checkout_add_ons_woocs_currency_support', 100);
add_filter('woocommerce_checkout_add_on_get_adjustment', 'wc_checkout_add_ons_woocs_currency_support', 100);