Google and TikTok may seem free, but every click and scroll you make gets packaged into a "user profile" and sold to advertisers. Take Facebook, for example—it makes about $50 per user per year just from their data. In the internet age, if you're not paying for the product, you are the product.
In the context of the phrase " the free things are the most expensive" I would have thought you will be talking about, water, air, oxygen and the rest of the free things God created for mankind. However in addressing the free things you listed, they are basically not free, these are people's businesses you mentored, for you to use their facility, you have to pay for it, those apps were not invented from the beginning to be use on free bases, for the inventor to build it and put it on the app store, he definitely paid for it to be there, so you the end user too will have to pay for it.
I was also thinking those free things aside the ones listed @spaceman {air, water, trees and on} would be kindness, love, forgiveness, friendship, happiness , peace and more. Google, tiktok, Facebook and more are business oriented if not from there beginning, at least for so many years now.
At the least of it, you need data to browse and that is cash.
And then subscription of one kind or the other.
Just name different ways that this platforms are doing their businesses making money..