Seoul denies paying a ransom for the hostages, but ABC News has learned the government paid the Taliban $950,000, or $50,000 per hostage.
The South Korean government does admit it agreed to pull out a small group of military engineers and medical workers and to end South Korean missionary work in Afghanistan in exchange for the hostages' release.
ABC News' Gretchen Peters in Pakistan and Hanna Siegel in New York contributed to this report.