Seventeen shekels of silver; i.e. about £2 5s. 4d. (taking the shekel at 2s. 8d.). This has been thought a small price. Thirty shekels were paid for the potter's field (Matthew 27:7); fifty by David, for Araunah's threshing floor and oxen (2 Samuel 24:4).
The Hebrew has "seven shekels and ten of silver;" hence the Targum increases the price by supplying "minas" before "of silver," bringing up the sum to one hundred and seven shekels. This, however, seems too much.
Even if Jeremiah wished to be liberal, he would hardly have been able to go so far (probably) in excess of the market price. Who would have purchased the land on speculation, if Jeremiah had refused?
The famine made life, the siege, a continuance of personal liberty, terribly uncertain. And, putting this out of the question, there may have been but a short time to elapse before the year of jubilee, when the land would revert to its original occupant (see above).
The singular form of expression in the Hebrew, at which the Targum stumbled, may, perhaps, be the usual style of legal documents.