What those pronouns represent?

The following passage is from the website as follows:

http://www.epubbud.com/read.php?g=H8AVF5J5&p=8

Each older man had a trading partner to the south whom he met once a year in the dry season at a ceremonial gathering. In exchange for a dozen sting-ray barbs, to be used as spear tips, he received an axe. In turn he had obtained some of the barbs from his other trading partner to the north – to whom he gave an axe in return. Another 150 miles to the south, the exchange rate was different: one axe for one barb. There were arbitrage profits all along the chain.

Let me give you more context to give you clearer view of this trade. Before the passage above there was a story of a tribe, the Yir Yoront aborigines, each of whose family camp had one highly valued stone axe, which all came from a quarry by the Kalkadoon tribe, far south beyond the Yir Yoront lands, and the axes passed through the hands of many trading partners to reach the Yir Yoront aborigines.

In the passage, ‘he’ of ‘whom he met,’ and ‘he’ of ‘he received an axe’ stand for ‘Each older man.’

The problem comes from next sentence, in a sense of context, the underlined ‘he,’ ‘his,’ and ‘he’ seems to represent the same ‘each older man,’ but in that case that doesn’t make any sense to me. He already exchanged an axe for 12 sting-ray barbs. How is it possible he exchanges ‘some of the barbs’ for his axe with the value of 12 sting-ray barbs. (‘Some’ in this sense means ‘a few,’ right?) He seems to be in a serious deficit in this trade.

Can you tell me how this happened, and what does each of these pronouns, ‘he,’ ‘his,’ and ‘he’ represent?