The theory that you're describing holds only if ads placed through Google Shopping outperform whatever other kind of ads might appear there. If the Google Shopp

The theory that you're describing holds only if ads placed through Google Shopping outperform whatever other kind of ads might appear there. If the Google Shopping ads (not actually the right term) actually perform worse, then Google will lose money, and the funding will not be unlimited. The product results that appear in Google Search are called Product Listing Ads (PLAs), and are not a comparison shopping feature today. (I don't know how things worked in the past.) They are simply advertisements. Individual merchants publish their product catalog into Google's Merchant Center, along with the price they're willing to pay for each product ad. It's similar to adwords, just with product information too (title, picture, price). Consequently, it's not a comparison shopping system - within Google Search it is purely an advertising feature with more information than text ads. Furthermore, as far as I'm aware, any company can participate in it by listing their products. I also think but am not positive that the only products featured in the carousel will be paid advertisements - another way in which it is not a comparison shopping system. Note: I'm only describing Product Listing Ads within Google Search results, not whatever else Google Shopping might be. It does appear that the main Google Shopping website also involves payment from merchants, which they disclose on the page. I don't know what determines whether the product carousel is displayed or not. I would assume that it's shown at the top when Google has enough information to display it, and when it's outperforming other types of ads. Anecdotally, Product Listing Ads have considerably higher conversion than traditional AdWords, so I would expect that PLAs will naturally perform better and would justify the top advertising slot.