Hypothetically, a channel with around 130 million views, like DNews, could expect to gain approximately 10 million views as a result of captioning (assuming the documented 7.32% increase).
The cost of captioning all of the content on DNews (about 1100 videos, each around 3 minutes long) would be approximately $8,250.
Assuming $1-$10 CPM, the 10 million expected views attributable to captioning would equate to earnings anywhere from $10,000 to $100,000.
In this case, the cost of captioning would be paid back and more: it could even provide over 10x return on investment.
(Keep in mind that this estimate is based only on views, and many other factors play into video monetization, including co-publishing videos on YouTube and your own website, engagement metrics, advertising, and implementing YouTube SEO best practices.)