CusRev is not a review aggregator for Google Shopping. We do not host an XML feed with your product reviews. However, you do not have pay to a review aggregator to get your reviews to Google Shopping. You can also create and host the XML feed with product reviews on your own site for free. Here is a section on Google's website that explains about it:
You can use our plugin (see Google Shopping XML Product Review Feed) to automatically create the XML feed with reviews. The plugin is able to create the XML feed with product reviews and update it every 24 hours. After you create the XML feed with reviews, please follow guidance on Google's website to submit them: https://support.google.com/merchants/answer/6059553. As of now, it is necessary to fill in a form to enable product ratings in your Merchant Center account.