Comment by patio11

Softbank (Japan) will buy it back from you. Yesterday they gave me $240 (structured as $10 a month for 24 months as a statement credit) for my iPhone 4S. (http://www.softbank.jp/mobile/campaigns/list/tada-kisyuhen/) Generally they're rather less generous ( http://www.softbank.jp/mobile/campaigns/list/shitadori/ )

I assume that Softbank processes 10,000 of these at a time and then sends them to China for resale.