The 'Keeping Up With The Kardashians' star splashed out the huge amount at auction on the gold Cartier timepiece, which was once owned by the former First Lady of the United States of America.
TMZ reports that Kim entered the auction as an anonymous bidder and more than tripled the expected selling price of $120,000.
The purchase comes just months after Kim, 36, insisted that being robbed at gunpoint in Paris, France last year has made her a more humble, less materialistic person.
She said: ''It was probably no secret, you see it on the show. I was definitely materialistic before, not that there's anything bad with having things and working hard to get those things. I'm really proud of everyone around me that's successful.
''But I'm so happy that my kids get this me, that this is who I am raising my kids. I just don't care about that stuff anymore. I really don't.''
The star - who has 18-month-old son Saint and three-year-old daughter North with her rap star husband Kanye West - also insisted the robbery had taught her some important life lessons.
Kim explained: ''I don't want to cry anymore. I really feel like things happen in your life to teach you things.
''Meeting with my attorneys and knowing the information that I know now, [the robbers] had been following me for two years.
''They had heard interviews that I did, getting excited about this jewellery and that jewellery. I truly don't know if I'd ever feel comfortable wearing jewellery anymore, or wearing real jewellery again.
''My whole life has changed in terms of how I travel and my security. I never thought I would need security staying outside of my door. I should have had a security guard outside of my door. Now I have several just for me to be able to sleep at night.''
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