In the opensource world, we go and give talks for free. This is generally the consensus with regards to the tech world as well. You don’t pay for speakers. Some speakers have fees and you somehow negotiate with them to provide you a talk for free. Or you just don’t have them speak at your event (I know this from organising large events too).
But paying for speakers must be common. There are so many speaker bureaus out there.
Look at Bill Clinton and Tony Blair. Now it seems that Timothy Geithner earned USD$400,000 for 3 speeches (seems his average is $100,000 per speech). Hillary Clinton charges USD$200,000 for a speech on average.
Clearly, I must be in the wrong industry.