The first farmer showed his grain to a merchant, who was so impressed with the grain that he bought the rights from the farmer to winnow, mill and bake the grain into bread and then sold the bread to shops, in return for a small amount of the sale of each loaf. The merchant made more money than the farmer, but had risked a great deal of his own money paying for winnowing, milling, baking and promoting the bread, while the farmers job essentially stopped after harvest
The second farmer, who had heard that merchants and grain agents were very picky about grain these days, really just wanted people to eat his wheat. He sometimes paid others to winnow mill or bake the grain into bread, sometimes did it himself, and negotiated himself with the shop owners. While he spent a lot of his own money and time, he kept all the money that the shopkeepers gave him, and all the money from the bread he sold himself. One year, his grain made fantastic bread which was so popular a merchant approached him for rights to his grain (see first farmer).
The third farmer was approached by a man who called himself a merchant, who praised his grain to the skies. He said it was just the grain he was looking for, and would be happy to pay the farmer for the rights to his grain. Only, wasn’t it fair that the farmer should contribute to the costs of winnowing, milling, baking and selling to the shops? The farmer, somewhat impressed that anyone would want to buy his grain in the depressed bread market, paid the merchant (who had many stories of how successful people had been making their own grain into bread). The merchant then promised the farmer that he would get a substantial proportion of the sales of the bread, and an even bigger proportion of the money he made from any he sold himself.
And when the other farmers heard about this they said “Dude, seriously, you’ve already paid them to winnow, mill and bake the bread that you’re selling yourself, why give them one red cent extra?”
The third farmer then found that the winnowing, milling and baking wasn’t much good. And, to be honest, his loaves were just plumped onto the shelves of big bread stores without any promotion, getting lost in the proliferation of loaves. In fact, if he tried selling any of that grain by himself, the merchant would tell him he couldn’t, he could only sell grain through the merchant (who was beginning to look a lot like Robert Carlyle in Once Upon a Time).
His “merchant” wasn’t bothered, as he’d already been paid, and actually made most of his money from charging farmers for processing their own grain.
And there were always more farmers desperate to get their grain made into bread.
 Actually, he first showed it to a grain agent, who was so impressed he agreed to negotiate the contract with the merchant for a consideration of the revenue, but that’s by the by.
 The merchant also paid for options on next years crop, and first refusal on any oats, barley, etc the farmer may produce, but that’s by the by
 He also paid for the rights to make and sell bread from previous years grain harvests. YOU SEE, THIS IS ALL A METAPHOR.