Understand who is actually selling
Most market stalls are run by one or two staff who take orders for a factory or another trader. The person behind the counter is rarely the manufacturer, and the price usually carries at least one layer of margin.
Buy with the shipment in mind
Market goods are packed for the counter, not for export. Agree repacking and labelling before you buy, and consolidate purchases from several stalls into one receiving point so the cargo can be shipped as one load.
Get receipts and facts on paper
Market deals move fast and cash-like. Record what was bought from whom, at what price and quality, and photograph the goods before they leave the stall — the record is what makes a later claim possible.