How sharing / hosting site earn money??

I see a lot of file hosting and sharing sites here. Like oron, hotfile, rapidshare. You can earn money for 1000 downloads. But how these sites earn money? not only advertising is too low. I have started a website like these for myself, just for fun. and I now have 5000 unique visitors a day. it must be possible to earn some money with this. Can someone explain to me how this sharing sites make money.
Kind regards,

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