Does anybody know what the rationale is behind companies paying these crazy sums to speakers? At first look it looks like a bribe to get better connections and treatment from people in or close to political power but is there a more charitable explanation? Does such a speech give deep insight that's worth the money?

My company sometimes has reasonably famous keynote speakers and I find these speeches either entertaining or boring but they never seem to produce much value. But I am just an engineer. Maybe business guys get more out of it?