Gatsby net worth: $1 Billion
Great Gatsby would only be worth $1.25 Million in 1922.
Which would only make $18.57 Million in 2020's Money.
Far from the Billion dollar claimed above.
I don't know if you watched the movie, but the Great Gatsby was literally flushing money down the toilet on a weekly basis throwing lavish parties for sycophants he didn't even know. All in the hope to catch the attention of Daisy, the love of his life he lost five years ago.
The prohibition being already over in the movie. As a former bootlegger, Gatsby probably struggled to keep his lifestyle with diminishing revenues.
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