What's the meaning of "They’ll be all the sense you got"?

On page 13 of Educated by Tara Westover, it says

When Dad read the verse to his mother, she laughed in his face. “I got some pennies in my purse,” she said. “You better take them. They’ll be all the sense you got.”

What's the meaning of "They'll be all the sense you got" here?

Solution 1:

Well, @lbf already quoted some of the relevant passage from the book, which shows it has nothing to do with 'penny wise and pound foolish' even though that is a lovely expression that plenty of Americans use without understanding that it's not really about a pound weight.

@KarlG was right in the comments above:

It's a snarky pun.

It ruins the humor to go step by step through the process, but I guess @Peace is really curious about the wordplay so let's do this.

First off, the fuller setup to the joke is Dad reads a passage from Isaiah—"Butter and honey shall he eat that he may know to refuse the evil and choose the good" (Dad still uses the KJV apparently)—which he reads four times with growing intensity and alertness before pronouncing it an obscured commandment from the Lord.

Second, the passage is actually a prophecy about the birth of a boy named Immanuel (Heb. for "God is with us") that Jews typically take to refer to Isaiah's attempt to get Judea's good-for-nothing king Ahaz to grow a pair and Christians invariably (owing to Matthew 1:23) take to refer to the supposed virgin birth of Jesus (né "Josh"). The author's family are Mormons and the LDS's official understanding of the bit about "butter and honey" is the same as almost every other earnest scholar's: it's an ironic use of the Torah's imagery of a prosperous "land of milk and honey" (Exodus 3:17 & Deut. 31:20) to describe the diet Judea will be left in the near future, when it will be forced to give up its rich stockyards and vinyards for the lousy fare of poor nomads (Isa. 5:9 & 7:22).

Instead of any of that, based on his faulty understanding of the KJV's faulty translation (it's closer to "curds", not "butter"; it's closer to "before", not "that"), Dad decides what the passage really means is that G-d is presenting His followers a choice between butter and honey, one which is godly and the other evil. He decides dairy farming is the work of Satan, bins everything lacteous in his fridge, and purchases a truly ridiculous amount of honey.

Grandma has other ideas. She and Dad "got along like two cats with their tails tied together" (i.e., with lots of hissing, screeching, and bared claws); she doesn't approve of the way he's raising the kids (viz., treating public education like it's the work of Satan); and she doesn't bite her tongue when she sees him up to more foolishness.

When he shares his "revelation" about the sinfulness of lactose and all its works, she just thinks it's his latest bout of idiocy and says so.

The joke works like this:

• From 1786, the official name of coins equal to one hundredth of the US dollar has been "cents", pronounced /sɛnts/.
• It's pretty common in all dialects of American English to drop /t/ sounds from the ends of words when they are followed by another consonant. It's especially common in less educated rural dialects. Thus, "cents" can easily be pronounced as /sɛns/.
• "Sense", also pronounced /sɛns/, has been a clipped form of "good sense" or "common sense" (i.e., basic intelligence) since Old French and Middle English.
• Dad has just tossed plenty of perfectly good food and drink into the trash and used up a good chunk of his savings to buy a ludicrous amount of honey. He has little cash at the moment.
• He has done this based on his belief that he (alone in 3000-odd years of scriptural exegesis) has unlocked a secret commandment of the Lord based on his unlettered understanding of an outdated English translation of a bad Latin translation of a Hebrew prophecy. He believes this in spite of the authoritative readings of his own denomination; in spite of numerous biblical passages supportive of dairy; in spite of his lack of the blessings biblically bestowed upon the Lord's true prophets; and in spite of the plain reading of the passage even in his own version.
• In Grandma's opinion, he's been prone to similar nonsense.
• He thus has neither sense nor cen's.
• Grandma is far past fed up with this and doesn't mind saying so, though she has her own wry humor in the face of the inanity her grandchildren are suffering through.
• It's too obscure for humor to simply say she has "cash" or "change" to lend him; it's too on-the-nose to say she has "cents". Instead, she goes one remove from the necessary term and uses "pennies" (not "pence"), which shows up in the KJV as a translation of the Romans' denarii and has been used as a common colloquial name for the American cent since the 1830s.
• If you noticed it, the odd grammar ("you got" instead of "you've got", &c.) is the author recreating Grandma's dialect, as well as showing that Grandma is using an informal and folksy register (which is what we do for humor most of the time) rather than a proper and formal one (which is usually too stuffy for any humor, let alone "lowbrow" jokes like puns).

To finish out the scene, it's worth noting that afterwards Grandma makes it a point of pride to buy all the dairy she can find, including every grade of milk ("skim... two percent, whole, even chocolate"): "Breakfast became a test of loyalty..."

Solution 2:

sense

A fuller excerpt:

The next morning Dad purged our fridge of milk, yogurt and cheese, and that evening when he came home, his truck was loaded with fifty gallons of honey.

“Isaiah doesn’t say which is evil, butter or honey,” Dad said, grinning as my brothers lugged the white tubs to the basement. “But if you ask, the Lord will tell you!” Biblehub.com

When Dad read the verse to his mother, she laughed in his face. “I got some pennies in my purse,” she said. “You better take them. They’ll be all the sense you got.”

Mother's meaning: He, the Dad, knows not of what he speaks. "Take the pennies". It will be all the cents (sense) he has. This is called a pun using cents and sense.