That’s very interesting! I’d also read somewhere that data collection was a trillion dollar industry, however the figure I found here is purely data brokerage so does not include Google per se - Google sell advertising, the data they collect is kept to themselves, so it’s much harder to pin down a value.
It also stands to reason that an American’s data is worth more on the market than, say, a North Korean’s - users who use the internet more will have more data being traded.