Gwendolyn Sontheim Meyer Net Worth: Gwendolyn Sontheim Meyer is an American heiress and equestrian who has a net worth of $3.3 billion. The great great granddaughter of Cargill Inc.’s founder William W. Cargill, Gwendolyn Sontheim owns 9% of the largest private company in the States, i.e., Cargill. She and five other relatives together hold the control of the $137 billion (sales) agribusiness firm, which is active food sale, crops procession, trading commodities and providing financial risk management. Meyer is not active in the day-to-day operations in the company, but instead spends her time at Coral Reef Ranch in Rancho Santa Fe, CA, where she owns and trains horses that compete in show jumping and dressage.