After struggling for a long time with this problem I found this fix -
<meta itemprop="price" content="<?php echo preg_replace('/[^0-9.]+/', '',strip_tags(Mage::helper('core')->currency($_product->getFinalPrice()))); ?>">Just insert above this line-
<span class="price"><?php echo $_coreHelper->currency($_price,true,false) ?></span>
All credit goes to -
https://feedarmy.com/kb/magento-microdata-for-google-shopping/
