[Symbiote]

People are discussing very different situations.

You're describing routine purchases in (perhaps) a market in West Africa, probably with few tourists around. The hawkers aren't making any money from dishonest sales to tourists, and sales are probably reasonably consistent. Repeat customers are common.

The others are describing very popular tourist areas in poorer parts of Europe. All their money comes from tourists, sales rise and fall frequently, there are no repeat customers, and there is strong competition between hawkers for the best places, and possibly efforts to keep newcomers out of the trade.