How much silver did Abraham pay Ephron for the field and cave of Machpelah?

Answer: 400 shekels

Abraham weighed out four hundred shekels of silver, the price Ephron had named, to buy a burial site for Sarah.

“Abraham agreed to Ephron’s terms and weighed out for him the price he had named in the hearing of the Hittites: four hundred shekels of silver, according to the standard of the merchants.”— Genesis 23:16 (BSB)