To a billionaire, this amount of money is nothing but a drop in the ocean.
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From Sima Qian's 《报任少卿书》 (Han dynasty): if he were executed, it would be "like losing one hair from nine oxen" - worth no more than an ant's life. Written after he chose castration over death to finish the 《史记》.
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Nine oxen × countless hairs each - losing one is imperceptible. English "drop in the bucket" captures the same ratio.