The good for sale is the parking space. If your vehicle is there without a receipt, using it without paying looks exactly like stealing unless you can show that the property owner allowed it. You can say that the payment system was broken but they’re just going to say that’s an excuse and you just didn’t want to pay, etc. – life is way too short to spend trying to argue things like that versus just going somewhere else. Most of the possible outcome involve you paying considerably more, and the ones which don’t are only cheaper if your time is free.
Yes, but if you want to compare it to a store then everything in the cart has to be something that will expire in an hour, and the shelves restock whether or not anyone buys them. And there's nobody around that can fix the self-checkout or check you out themselves.
> life is way too short
I'm only here to talk about the analogy you made, not give advice on parking.
None of which changes the fact that you can’t use property which doesn’t belong to you except on the owner’s terms unless there’s some kind of legal right such as the “right to roam” laws in many European countries. There is no right to store your car without paying for it so there’s no gray area here.
It’s theft of service, which is definitely not identical to theft of property but I think the analogy is useful because more people understand that a business screwing up doesn’t mean you get their products for free - it means you go somewhere else.
It especially doesn’t mean you have any expectation not to be treated poorly by that business the way you would if you’d complied with your side of the legal agreement. If you’d paid and the business failed to track that payment properly, you’d be getting serious compensation because there would be a legal contract they weren’t honoring.