Ah true, for US users it would be a lot higher. Seems to be around $10 billion per quarter of revenue for US and Canada[1], which means around 15 per user (for around 250 million users[2]. You weren't that far off! That's definitely a lot more than what the gut feeling I had was (which is why I just googled the first stat that seemed to align with my hunch - classic mistake).
1: https://www.statista.com/statistics/223280/facebooks-quarter...
2: https://www.statista.com/statistics/408971/number-of-us-face... + ~20 for canada