Apparently, it's worth about 18.7 cents per month per individual.
And that's assuming it was even effective and not just the technological equivalent of casting bones, which experts are pretty certain it was.
Chaos monkeys has a good epilogue where the author talks about the Trump campaign in 2016. His take on it is that Cambridge Analytica specifically was basically just reading tea leaves. But it's indicative of the larger pattern that the Trump campaign was spending huge piles of money on getting the word out and polishing the image of their candidate, far more than the opposing campaign. The opposing campaign bet on Trump being so unlikable that they could save the money and move it down. Ticket to reinforce Democratic candidates other than the president.
They lost that bet, and the outcome of the election is far more explainable by simply asking where money was spent for classical, legal advertising then by invoking any kind of unproven technology that appears to have really not moved the needle in hindsight analysis.
By all means, Facebook can and should be smacked for breaking the law regarding how people's trusted information was moved around. But make no mistake, 0% of this fine is because they illegally disrupted an election.