Помог плагин на событие OnSHKgetProductPrice
<?php
$output = 0;
if(!empty($_POST['itemPrice']) && is_numeric($_POST['itemPrice'])){
$output = $_POST['itemPrice'];
}else{
$price_tv_name = 'price';
$p_id = isset($purchaseArray['shk-id']) && is_numeric($purchaseArray['shk-id']) ? $purchaseArray['shk-id'] : 0;
if($p_id){
$price_tv = $modx->getObject('modTemplateVar',array('name'=>$price_tv_name));
$output = $price_tv->renderOutput($p_id);
}
}
$modx->event->_output = '';
$modx->event->output($output);
return '';
