Just like auction houses - it's a winner takes all. The biggest exchange has the hughest volume and lowest spread. As for competitors lowering their fees - one

Just like auction houses - it's a winner takes all. The biggest exchange has the hughest volume and lowest spread. As for competitors lowering their fees - one can onlly do it as long as it has funding to do so. Here you can witness a perfect example of a free market economy leading to a suboptimal situation. And an example of usefullness of antitrust laws.