James Jordan offers this argument to conclude that only firstborn between the ages of one month and five years died at Passover:
1. The redemption payment for the excess number of firstborn, when the Levites replaced them, was five shekels apiece (Numbers 3:46-48.
2. In the redemption schedule in Leviticus 27, five shekels is the redemption price for a male “from a month even up to five years old” (Leviticus 27:6).
3. He also makes the commonsensical statistical argument that the number of firstborn would have been far larger than 22,273 if every firstborn child were counted. If there were 600,000 men 20 years old and upward, and assuming half were married with children, and that half of them had firstborn sons , we’re talking 150,000 firstborn.