The development costs of SL were heavily subsidized by FreeCreditReport.com, GoDaddy.com, and several Cayman Islands based Viagra and Cialis retailers, in exchange for heavy banner ads, interstitials, and other product placement in SL. The catch is that Apple really needs to sell SL for them to pay the full amount pledged.
Don't forget the Nigerians that just inherited millions of dollars and just need Apple's account number.