<?php

add_action( 'tribe_eb_after_event_creation', 'my_change_tribe_eventbrite_currency', 10, 4 );

function my_change_tribe_eventbrite_currency( $eventbrite_id, $venue_id, $organizer_id, $post_id ) {
    // See http://www.currencysystem.com/codes/ for a list of three-letter
    // currency acronyms. Change the below variable to your preference.
    $currency_acro = 'EUR';

    $parameters = 'id=' . $eventbrite_id . '&currency=' . $currency_acro;

    $success = Event_Tickets_PRO::sendEventBriteRequest( 'event_update', $parameters, $post_id, true, true, false );

    if ( !$success ) {
        add_filter( 'tribe_eb_error_message', 'my_change_tribe_eventbrite_currency_failed' );
    }
}

function my_change_tribe_eventbrite_currency_failed() {
    return 'Failed to update the currency.';
}