Its simple and nice...
There should be a point system. Points can lead you to getting you able to download some files. To earn points, you can do it by these actions...
-Upload A File (10 Points)
-Download A File (1 Points)
-Someone Downloads Your File (1 Points)
-Points From Other People (If they download a file, that costs some points and you get those points.)
-Donating (Depends, on how much money they donate...)
You can make a file having a point cost, but the points cost is very limited. Its sort of a currency system.
Plus there should be a highscores system on who has the most points...
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