Actually the price was very close to market price: $52.50, market price at the time was $50.72. I suspect that Herbalife didn’t want all those shares hitting the market at one time. Before the sale, he had a 26.2% stake. Icahn’s supposed average cost was $21.03/sh. Not too chabby.
Icahn claims that it was representing too large a share of his portfolio, so he reduced the holdings to balance.