pearl of great price
The expression has come to mean anything that is very valuable. For example, Hester Prynne, in The Scarlet Letter, who gave birth to a daughter following an act of adultery that destroyed her honor, named the child Pearl, because she had given up all that she had in bearing the child.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.