I admire how simple you made it.
'Go somewhere else if the vendor overpriced it.'

But what if its a product that's in scarcity
My country Nigeria is a peculiar one that even things like food could be scarce and therefore in high demand. And there is no alternative vendor to patronize, what would you do?

There was even a time when the currency(Naira) was scarce and citizens had to buy it at overpriced amount cos they had no choice