Event Espresso 3, send payment confirmation email to the admin too. Add this function to the site's /wp-content/uploads/espresso/custom_functions.php file

custom_functions.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

if (!function_exists('event_espresso_send_payment_notification')) {

	function event_espresso_send_payment_notification($atts) {

		do_action('action_hook_espresso_log', __FILE__, __FUNCTION__, '');

		global $wpdb, $org_options;
		//Extract the attendee_id and registration_id
		extract($atts);
		
		$registration_id = is_array( $registration_id ) ? $registration_id[0] : $registration_id;
		
		if ( empty( $registration_id ) && isset( $attendee_id )) {
			$registration_id = espresso_registration_id($attendee_id);
		}
			
		if ( empty( $registration_id )) {
			return __('No Registration ID was supplied', 'event_espresso');
		}			

		//Get the attendee  id or registration_id and create the sql statement
		$SQL = "SELECT a.* FROM " . EVENTS_ATTENDEE_TABLE . " a ";
		$SQL .= " WHERE a.registration_id = %s ";
		$attendees = $wpdb->get_results( $wpdb->prepare( $SQL, $registration_id ));

		if ($org_options['default_mail'] == 'Y') { 
			foreach ($attendees as $attendee) {
				event_espresso_email_confirmations(array('attendee_id' => $attendee->id, 'send_admin_email' => 'true', 'send_attendee_email' => 'true', 'custom_data' => array('email_type' => 'payment', 'payment_subject' => $org_options['payment_subject'], 'payment_message' => $org_options['payment_message'])));
			}
		}

		return;
	}

}