Tommy Tainant as you know, or may not know, we have the Sale & Supply of Goods Act in the UK. The way shopping works is, the retailer/law gives the right to treat. That allows customers to wander, look at, pick up goods, and decide if they want to buy. If this wasn't in place, as soon as someone touched an item, the shop owner could say, "You've touched it, you've bought it".
So items must have a clear price, but, you are under no obligation to pay that price, you could offer a lower price, or the stupid could offer a higher price. Then it's up to the shop owner to decline or accept your offer by ringing the payment through the till.
Many moons ago, a customer wanted to buy a bike, I said yes. He wanted a different seat and handle bars. I declined the sale.
Also, customers falsely believe, "It's on the shelf at that price, you must sell it to me". Wrong. I accept the £5 item sale, ring it in the till and it should have been £25. So sorry, I'm removing them off the shelf, refusing the sale and placing them to one side pending a price check audit.
So yes, I accept the sale of the cake, let's go down to the till, after discussing the design, "Ah, sorry, not something we do, I decline your offer to make a contract of sale and I don't accept payment. Have a good day".
How it works in America, no idea.
Tommy, I agree to buy your house. Two weeks later, I pull out. Tough, unless you live in Scotland, an offer on a house is legally binding. "But but, you said you would buy my house". How many house sales fall through !!