It's even more direct. The diversifications
are Google Ads, in a very real way. Google financial reporting splits Google ads revenue in an important way that hopefully allows people to see this. Total revenue of Google AdSense, on the non-Google internet, is about 7 billion. Nice, but Youtube ads is ~10% less than that ... and Google's own properties get 5 times more than that in ad income. Ads income from non-Google properties is called "Google network", ads income from Google properties is called "Google Search & other" in the financial reporting.
That's not even counting money someone actually paid to those diversifications, no ads involved. That's another 10-15% of the total ad revenue.
Google's internal websites, taken together, are just shy of 85% of their total ad revenue, and 90% of their total revenue. Google does not make that much money from people browsing the internet, it makes money from people browsing Google. Although not split out, it is widely assumed Google search is a whale here. But how much exactly? Not clear. People keep saying it's going down for a decade now. And of course, a business 1/10th as good as Google search is still a great business.
Yes, Google Ads receives the dollars, but it's the "diversifications" that "only cost money" that brings them in. Numbers like this make one thing clear, 7/8th of AdSense is a way to optimise ad income on Google's own websites, and only 1/8th of AdSense is an actual Ad Network. Google is not the biggest Ad Network, despite their reputation, by a very wide margin. Google is the biggest "TV Network".
So saving money on diversifications as a whole ... I'm going to say this is not what I'd like Alphabet to do. Now saving money on specific efforts, sure. But, frankly, the way to grow Google, even their ad business itself, it to spend more money on the diversifications.