<?php
...
case 'msOnGetProductPrice':
	$data = $modx->getOption('data', $scriptProperties);
        $product = $modx->getOption('product', $scriptProperties);
        $product_id = $product ? $product->get('id') : $data['id'];
	$field = $modx->getObject('cfField', array('city_id' => $cityFields->currentCityId, 'placeholder' => '[pre]'.$product_id.'_price[/pre]'));
	if ( !is_null($field) ) {
		$values = & $modx->event->returnedValues;
		$returned = $modx->getPlaceholder('_returned');
		$returned['id'] = $product_id;
		$modx->event->returnedValues['price'] = $returned['price'] = $field->get('value');
                $modx->setPlaceholder('_returned_price', $returned);
		if(is_object($product))
			$product->set('price', $returned['price']);
		}
	break;