The Accra street vendor looks at me, bemused.

I'm trying to establish how the rather flimsy 30g bag of roasted cashew nuts she's selling, beside a sweltering highway in Ghana's capital, costs me the equivalent of about 75 cents (60p).

That's obviously not a lot of money for me, a visitor from the UK, but I'm amazed at the mark up.

The price is at least 4,000% higher than the cost of buying the same weight of raw, unshelled cashews from a Ghanian farmer.

"It's incredible," I protest. Yet she doesn't understand my English, or my reasoning.

The price of the nuts was, after all, printed on the packet. And explaining why I thought it was beyond the pale was never going to be easy.

Ghana is the world's third-biggest exporter of unprocessed cashew nuts, behind Ivory Coast in first place, and Cambodia in second.

To produce the crop, around 300,000 Ghanaians make at least part of their living growing cashews.

Nashiru Seydou, whose family have a farm in the country's north-east, some 500 miles (800km) from Accra, is one of them.

He says the work is hard, and unreliable supply chains and volatile wholesale prices make survival difficult.

"We are struggling. We can use the sunlight, the fertile land, to create more jobs," he says. "I'd be happy if the government comes to our aid and helps support our industry."

He tells me that he currently gets around $50 for a large 100kg sack of unshelled cashews.

"It's amazing," says Bright Simons, an entrepreneur and economic commentator in Accra, who has studied the numbers. "Roasters and retailers buy the nuts from farmers for $500 a tonne, and sell to customers [both at home and abroad] for amounts between $20,000 and $40,000 a........

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