Jew’s eye

a popular simile for anything valuable. Probably a corruption of the Italiangioje Frenchjoaille , a jewel. In ancient times, when a king was short of cash, he generally issued orders for so many Jews' eyes , or equivalent sums of money. The Jews preferred paying the ransom, although often very heavy. It is notorious that in this country the order often went forth to draw Jews' teeth in the event of their refusing to contribute so much to the Exchequer. A probable idea is, that as a Jew's teeth brought in so much money, the value of a Jew's eye  must be something fabulous. Possibly, also, from the lex talionis  so strongly believed in by Jews,—an eye for an eye, and nothing less. The term is used by Shakspeare.