auth/register: tokens_instance_cost 7200 > 1800

pages.php

@@ -22,7 +22,7 @@ define('PAGES', [
 			'title' => _('Create account'),
 			'description' => _('Create a new account, and log in with it'),
 			'require-login' => false,
-			'tokens_instance_cost' => 7200,
+			'tokens_instance_cost' => 1800,
 		],
 		'unregister' => [
 			'title' => _('Delete account'),