True, and not all monopolies are illegal. Certainly not a cut and dry discussion. In many cases, these exchange fees have been in place for quite a while, but brokers were hiding those fees as long as you maintained a certain amount of trading activity.
I have certainly witnessed a steady increase in exchange fees (especially futures markets) that seem to have coincided with market consolidation. However, I would think that as a futures trader, the covering of said fees would be more than covered by 1 good trade) even as a retail trader.
Here's a slightly amusing example of the strength of liquidity attracting liquidity.
http://www.reuters.com/article/us-cme-cocoa-idUSBREA400FW20140501
http://www.wsj.com/articles/cme-def...ntract-against-industry-complaints-1453814477
Now go look at CME cocoa volume today. A big fat zero.