That's exactly right-- some are even calling Amazon's ad offerings "new slotting fees," as virtual shelf space becomes more valuable: https://econsultancy.com/is-amazon-s-ad-business-the-new-slotting-fee/ So we may see a higher barrier to entry for new products getting eyeballs online, particularly on Amazon. As for supermarkets, it would make sense for them to try to eke out a little more profit by increasing prices on products (if they're no longer getting the money from slotting fees), but this space is so competitive I imagine it would be difficult to increase prices by much. To quote Bloomberg, "It’s a battle over a few pennies on the price of milk, mustard, detergent, and barbecue sauce—and perhaps the future of groceries." There are even apps for people to compare grocery store prices, and that sort of price transparency will likely keep prices somewhat in check: https://money.cnn.com/2016/09/06/technology/basket-shopping-app/?iid=EL

Thanks Justine. The EU is already preliminarily looking into Amazon's anti-competitive behaviours as it has access to all the sales data on 3rd party sellers on the platform, and if a product is selling really well, they can just create a similar product at a lower price and push their own products on the platform.