Selling below cost and locking down the market

[Edax]

I don't understand why someone would sell below the cost for an extended long period of time. I mean, crafting is for making a little profit and Gil, right? or not? I don't understand what's going on... How normal is for someone to flood a big part of the market without making a profit? Or, is there something I miss?

John D. Rockefeller became the wealthiest American of all time and one of his tactics was to price his products below the manufacturing cost to destroy his competition. He had the money to weather the short-term profit loss and by out spending his smaller competitors, he was able to maintain his extremely profitable monopolies.