When you export your data to the Google Shopping feed format, the values of the price and sale_price fields depend on whether Shopify's compare-at price field is set.
Going forwards, if the compare-at price in Shopify is zero, the app will treat that the same as if the compare-at price was not set. This will prevent prices of zero from unintentionally making their way into the Google Shopping feed.
Learn more about the Google Shopping feed format for Shopify.
