So who is in the wrong here?

Always make sure you check the date on the shelf tag. If it says the promotion is still valid, or if there is no date, you can point that out and get the price you wanted,

But most customers don't bother to check the dates.

If you're not sure -- if you can't see a date -- ask to speak to the grocery manager.

It is an inconvenience when that happens. The tag should also have a sale end date on it, or you get the sale price.

You are wrong, sweetie.

They can change the price right up until you complete the purchase.

In legal terms, no contract is formed until there is invitation, acceptance  and payment.  

In effect what happens when they scan at the till, the invitation is changed, and you can either accept, or walk away.

If the tag actually says $2, that’s what you should pay. If the store forgot to change it, that’s their problem not yours. Often times, the customer is not reading the correct tag though. It’s the store’s responsibility to advertise correct prices.

I'd give the store a break--they may not have enough personnel to make sure that every single promo price is removed once the promo is over. You can TRY to get the two jars at the promo price, since they WERE still listed on the shelf that way--but the store doesn't have to give them to you at that cost. Still, it doesn't hurt to ask. 

But JUST ASK. Don't 'demand.' 

You should go to a different store if this happens to you a lot.  Most stores make correct pricing a priority, and would give you the 2 for $4 price.

You pay what the shelf tag says. Thems the rules. Too bad if he forgot to change the tag.

Almost all the tags in very small print have the dates they are valid. Its fine to ask for the price but they don't have to legally give it to you so don't hold your breath.

Best to buy Jif in larger sizes at Sams or Costco. Costco was out of Creamy last time I was there.

Assuming you get your $2 price, its 12.5 cents per ounce. Sams & costco everyday prices are $8.99 for 96 oz or 9.36 cents an oz. And Costco used to have $2 off 2-3 times a year back before the pandemic.

I am not a member, I go in with a gift card and I can shop for the day. Have a member buy them for you or find an ebay seller.

I think you should buy Skippy.

The store has the legal right to correct the price tag.  

They are not obligated to sell you the peanut butter for an incorrect price just like an auto dealership is not obligated to sell you a $30,000 car for $3000 if the ad was printed incorrectly.

That being said, when the price difference would not create a hardship for the merchant, it's generally considered an investment in customer trust to honor the peanut butter price that was posted. 

On the flip side, it's generally considered impolite for a customer to hold up the line bickering about thirty-three cents.

If you are shopping at a store where the prices routinely ring up higher than the posted prices and it seems like an intentional ploy, that's illegal and should be reported to your state attorney general's office.   Convenience stores are notorious for this because they don't have the same kinds of registers that show the item name and price as it rings up and they won't offer you a receipt unless you ask for one.