This is an interesting quote, and I can see how different people might have different interpretations. My own thought about this is that a man who is squatting on his heels has endless patience and is prepared to stay in that position for hours to out-last the person trying to do a deal with him. I also see a kind of primitive aspect to a man squatting on his heels, someone who might not be well-versed in the kind of trading that goes on in the modern world, but someone whom the other cannot fool because the man is old and wise in the ways of trading.
Another thought I will share with you about interpreting quotations is that sometimes it is good to know something external to the quote. For example, who said this? Where? When? Sometimes, if we can situate a quote in history, we can find clues to its meaning.
I should point out that there is disagreement among people about whether or not it is "playing fair" to go outside a reading to interpret the words. This is an issue that will probably never be resolved. Should we just look at a group of words and based only on the words decide what they mean? Or should we be allowed to go looking for clues about the author, the time, or the place in which the words were written?
I am fairly certain that different people will have different reads on the quotation. It seems to me that answering it can be done in exploring its literal meaning and then its symbolic meaning. The image of a man squatting on his heels to talk to someone implies that it is very difficult to do such a thing. Merely thinking about such a situation conjures up a picture of a man having to do endure a great deal... simply to talk to another person. This would be the literal meaning. The symbolic, or deeper, understanding is that when someone is willing to endure so much for so very little, it should be acknowledged, respected, and perhaps, revered. It certainly should not be something where one discards it or "trades." One should acknowledging the lengths someone will go to in exchange for very little. In my mind, this is what the quote conveys.