Microdata error on product module

echo '<span class="'.implode(' ',$classes).'" itemprop="price" content="'. $price->price_value_with_tax .'">';

$attributes = '';
			if(!empty($this->element->product_id)){
				$round = $this->currencyHelper->getRounding($price->price_currency_id, true);
				$attributes = ' itemprop="price" content="'. $this->currencyHelper->round($price->price_value_with_tax, $round) .'"';
			}
			echo '<span class="'.implode(' ',$classes).'"'.$attributes.'>';