A.T. Robertson Commentary Matthew 16:26

"For what shall a man be profited, if he shall gain the whole world, and forfeit his life? or what shall a man give in exchange for his life?" — Matthew 16:26 (ASV)

Gain (κερδηση) and

profit (ζημιωθη). Both aorist subjunctives (one active, the other passive) and so punctiliar action, condition of third class, undetermined, but with prospect of determination. Just a supposed case. The verb for "forfeit" occurs in the sense of being fined or mulcted of money. So the papyri and inscriptions.

Exchange (ανταλλαγμα). As an exchange, accusative in apposition with τ. The soul has no market price, though the devil thinks so. "A man must give, surrender, his life, and nothing less to God; no ανταλλαγμα is possible" (McNeile). This word ανταλλαγμα occurs twice in the Wisdom of Sirach: "There is no exchange for a faithful friend" (6:15); "There is no exchange for a well-instructed soul" (26:14).