The test had one price. Targum Pseudo-Jonathan on Genesis 42:34 states it through the brothers' retelling: "bring your youngest brother to me, and I shall know that you are not spies, but faithful. I will (then) restore your brother to you, and you shall transact business in the land."
Why Benjamin specifically?
The Egyptian ruler — Joseph — is asking for the only other son of Rachel, his full brother. The rabbinic tradition in Bereishit Rabbah 91:7, a commentary on Genesis compiled in the Land of Israel around the fifth century CE, reads this as the completion of Joseph's emotional accounting. His last memory of his full brother Benjamin is of a young boy back in Hebron. Joseph is now thirty-nine. He wants to see Benjamin alive, in his presence, under his own eyes. But he cannot ask directly without revealing himself, so he disguises the longing as a test: bring the youngest, or you are spies.
The reward structure
Notice what Joseph promises in the same breath as the demand. Restoration of Simeon. Permission to "transact business in the land" — ongoing trade rights during the famine. The Aramaic paraphrase, whose final redaction belongs to the Land of Israel around the seventh or eighth century CE, preserves the full offer: comply once, and you have a permanent channel to Egyptian grain. It is a test dressed as a contract.
The takeaway
Joseph's condition reveals what he actually wants. Not grain money. Not spy intelligence. His little brother, standing in front of him. The test is a love letter in the form of a demand.