Where Does Blogger CMS Or Blogger.com Get Money To Maintain Itself?

Blogger CMS does not make money but Google does. Blogger is owned by Google, its development expenses are burned by the company. 

(Blogger.com Image)

Google's income comes from various sources, mobile apps, marketplace, business tools, ads, cloud storage, the list goes on and on. Google's incomes cover the cost to maintain Blogger, partially coming via advertising through Adsense. To optimize advertising in search, it needs content and lots of them!

This way, ads can be optimized to a more targeted audience - Advertisers become happy as the promotion results are what they are expecting.

This is where Blogger comes into the picture, as more and more content is published by users - more quality ad space for Adsense. In return, Blogger users can apply a bit easier through the Adsense Hosted Partner account via the Earnings panel - once they are eligible.

A blog owner gets part of the income for ads and the rest goes to Adsense/Google.

Hopefully, you'll get the idea of how a company makes money while still providing free services or tools, as the income to cover these costs comes from other related services/sources.