Google announced that starting on April 6, 2021 it will begin to enforce that the price fed to Google in the Merchant Center feed is not lower than what is displayed on the checkout screen. This is in addition to price enforcement validation of the price in the feed and on your landing page.
Google wrote "beginning April 6, in addition to reviewing and enforcing price accuracy between your Merchant Center product data and your landing pages, we will begin to review and enforce price accuracy at checkout." If the price is higher on the checkout page, Google said "you will receive a 28-day warning to resolve these mismatches, otherwise your account will be subject to suspension at the end of the warning period."
This has always been the rules of being in the Google Merchant Center but I guess some are not playing by the rules.
You should not be surprised by this, we knew Google was working on this. In July 2020, Google spoke about how GoogleBot can add items to your shopping cart. Then they told us this was to validate the price in the cart, as compared to what was on your landing page. But now, now Google will enforce it.
I am not sure how many e-commerce sites have to worry about this. I am not sure how big of an issue this is for Google. But I guess this happens enough for Google to have to take action in an automated fashion.
Forum discussion at Twitter.
