Just to be picky, the broker works for...the broker! If they can screw somebody to their benefit, they will.
Take a sellers broker. You'd think they would want to get you the best price so they get the most out of their 10%. NOT. They want the quickest sale they can arrange. Dropping the price 20% costs them very little but can accelerate the sale. You get screwed.
As for rates, 'round here the rate is 10% with a minimum. I saw minimums from $1500 to $2500. This makes the situation even worse. Lets say you are selling a $15,000 boat. 10% is $1500. The broker may have a $2000 minimum so he won't care if the boat sells for $10,000 if you agree to the $2000 minimum. He then tries talking you into the lowest listing price he can sucker you into. He's guaranteed his $2000 no matter what.