If one is familiar with the Scriptures one realizes that purchasing was done by weight (Ex. 38.26) and the number of pieces was determined by the weight of the purchase.  

Note: a shekel is a weight, 17 shekels would be approximately 30 average size silver pieces. ( https://www.biblehistory.net/Jeremiah_prophet.pdf - John Argubright)  

Zechariah 11:12-13 - And I said unto them, If ye think good, give me my price; and if not, forbear. So they weighed for my price thirty pieces of silver. And the LORD said unto me, Cast it unto the potter: a goodly price that I was prized at of them. And I took the thirty pieces of silver, and cast them to the potter in the house of the LORD. 

Most critics don't understand what a shekel was, and the actual differences between Israel's shekel and Babylonian shekel weights and the calculations.  

The original Jewish silver 1 Shekel = 14.55 grams derived from Exodus and Ezekiel.

See jewishencyclopedia article at https://www.jewishencyclopedia.com/view.jsp?artid=81&letter=W . Read under the bold headings "The Mina" and "Money" 

Jeremiah lived in Israel during the time of the Babylonian Empire. The Babylonian common heavy shekel weight was 16.37 grams, the Babylonian common light or half shekel weight was 8.19 grams. 

14.55 grams (Israel's shekel weight) x 17 shekels = 247 grams

8.19 grams (Babylonian common half shekel weight) x 30 pieces = 246 grams  

As you can see, it's right on the money.

“Intellectual” critics of the Bible say that Matthew 27:9 is in error because the 30 pieces of silver fulfillment was in Zechariah 11:13 not in Jeremiah 32:9, But it is actually a fulfillment of both passages. Now if  one possess wisdom and can get grasp this, perhaps one might come to realize the more important aspect, that is, God’s primary message of “redemption” was being declared here, rather than being “blinded” by a “lawyers” misconception of a number, which may cause the message of redemption to elude the unbeliever. 

Mark 4:9-17 - And he said unto them, He that hath ears to hear, let him hear. And when he was alone, they that were about him with the twelve asked of him the parable. And he said unto them, Unto you it is given to know the mystery of the kingdom of God: but unto them that are without, all these things are done in parables: That seeing they may see, and not perceive; and hearing they may hear, and not understand; lest at any time they should be converted, and their sins should be forgiven them. And he said unto them, Know ye not this parable? and how then will ye know all parables? …The sower sows the word. …And these are they likewise which are sown on stony ground; who, when they have heard the word, immediately receive it with gladness;  And have no root in themselves, and so endure but for a time: afterward, when affliction or persecution arises for the word's sake, immediately they are offended.  

2 Corinthians 4:1-4 - Therefore seeing we have this ministry, as we have received mercy, we faint not; But have renounced the hidden things of dishonesty, not walking in craftiness, nor handling the word of God deceitfully; but by manifestation of the truth commending ourselves to every man's conscience in the sight of God. But if our gospel be hid, it is hid to them that are lost: In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them. 

Luke 12:10 -  And whosoever shall speak a word against the Son of man, it shall be forgiven him: but unto him that blasphemes against the Holy Ghost it shall not be forgiven. 

Isaiah 55:6 -13 - Seek ye the LORD while he may be found, call ye upon him while he is near: Let the wicked forsake his way, and the unrighteous man his thoughts: and let him return unto the LORD, and he will have mercy upon him; and to our God, for he will abundantly pardon. For my thoughts are not your thoughts, neither are your ways my ways, says the LORD. For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts. For as the rain comes down, and the snow from heaven, and returns not thither, but waters the earth, and makes it bring forth and bud, that it may give seed to the sower, and bread to the eater: So shall my word be that goes forth out of my mouth: it shall not return unto me void, but it shall accomplish that which I please, and it shall prosper in the thing whereto I sent it. For ye shall go out with joy, and be led forth with peace: the mountains and the hills shall break forth before you into singing, and all the trees of the field shall clap their hands. Instead of the thorn shall come up the fir tree, and instead of the brier shall come up the myrtle tree: and it shall be to the LORD for a name, for an everlasting sign that shall not be cut off. 

The Word of God will always be a challenge for “intellectuals,” those who consider themselves “wise in this world,” and will almost never accept that what Jesus proclaimed about the Kingdom of God.

John 6:63 - “It is the spirit that quickens; the flesh profits nothing: the words that I speak unto you, they are spirit, and they are life.”  

1 Timothy 6:1-21 - Let as many servants as are under the yoke count their own masters worthy of all honor, that the name of God and his doctrine be not blasphemed. And they that have believing masters, let them not despise them, because they are brethren; but rather do them service, because they are faithful and beloved, partakers of the benefit. These things teach and exhort.

If any man teach otherwise, and consent not to wholesome words, even the words of our Lord Jesus Christ, and to the doctrine which is according to godliness; He is proud, knowing nothing, but doting about questions and strife's of words, whereof cometh envy, strife, railings, evil surmising, Perverse disputing of men of corrupt minds, and destitute of the truth, supposing that gain is godliness: from such withdraw thyself.

But godliness with contentment is great gain. For we brought nothing into this world, and it is certain we can carry nothing out. And having food and raiment let us be therewith content. But they that will be rich fall into temptation and a snare, and into many foolish and hurtful lusts, which drown men in destruction and perdition.

For the love of money is the root of all evil: which while some coveted after, they have erred from the faith, and pierced themselves through with many sorrows. But thou, O man of God, flee these things; and follow after righteousness, godliness, faith, love, patience, meekness. Fight the good fight of faith, lay hold on eternal life, whereunto thou art also called, and hast professed a good profession before many witnesses.

I give thee charge in the sight of God, who quickens all things, and before Christ Jesus, who before Pontius Pilate witnessed a good confession; That thou keep this commandment without spot, unrebukeable, until the appearing of our Lord Jesus Christ: Which in his times he shall show, who is the blessed and only Potentate, the King of kings, and Lord of lords; Who only hath immortality, dwelling in the light which no man can approach unto; whom no man hath seen, nor can see: to whom be honor and power everlasting. Amen.

Charge them that are rich in this world, that they be not high-minded, nor trust in uncertain riches, but in the living God, who gives us richly all things to enjoy; That they do good, that they be rich in good works, ready to distribute, willing to communicate; Laying up in store for themselves a good foundation against the time to come, that they may lay hold on eternal life.

O Timothy, keep that which is committed to thy trust, avoiding profane and vain babblings, and oppositions of science falsely so called: Which some professing have erred concerning the faith. Grace be with thee. Amen.