Variantly: R. Shimon b. Yochai says: An analogy: A man inherits a country-seat across the seas and he sells it for a pittance — whereupon the buyer goes and digs in it and finds in it treasures of silver and of gold and precious stones and pearls — whereupon the seller begins "choking." Thus with Egypt. They sent without realizing what they were sending, viz.: "What is this that we did, etc."
Egypt's Failure Was Not Just in Undervaluing Something Beautiful
Mekhilta Tractate Vayehi Beshalach 2:24