How much is potato worth to you right now? What about if you were full? And if you haven't eaten for 3 weeks?

So, do things even have an objective price?

No, we're ready to pay the price, no matter what it is, if we have enough money AND if we can't get the thing that we're buying elsewhere for cheaper.

If you live in the developed world you probably spend less than 50% of your income on your needs (food, shelter, electricity, water). You can spend the rest for your wants. This is probably more money than selling price of most of the things that you're considering buying. This leaves us with the second part of the equation.

You're always buying the cheapest thing that will satisfy your wants. If you believe that only a specific thing will satisfy them, you will pay the asking price. From your standpoint, a thing doesn't have a competition.

This means that marketers did their job.