The value is given to it by the users. The price in USD is determined by supply and demand. The market cap is just a useless number in USD, as far as I know. It's just the average value of one unit times the amount of units.
The value of Google is given to it by the users as well. If no one uses it, the value goes to zero and so does the price of the shares. Value is not what is it worth in USD. That's just the price. Price and value is not the same.
Google also doesn't "produce" any cash. The central bank does. Google just takes a part of it by producing ads and selling them.
The concept of Steemit is a bit different. It produces Steem - not Dollars. Steem is generated by the Steem network - not by a central bank. When you cash out, what you do is to exchange Steem for fiat currency, like Google when it sells an ad. The difference is that you can't use the ad or Google stocks to buy something else.
Thank you! @fieldsofgold