So I got asked the following in an email from a non-cyclist friend today:
What is the benefit of a multi-thousand dollar bike over, say, a $500 bike? If its sole benefit is to go faster for a given amount of pedaling effort, that seems counterproductive. If the purpose of biking is exercise, reducing the effort defeats the purpose. OTOH, if you expend the same effort on a $5K bike as a $500 bike, you’ll go faster, which is both more dangerous and reduces your enjoyment of the scenery because you’re whizzing by so fast.
My diplomacy skills fail me. (This guy is spending > $5K on recreational audio equipment, so the issue isn't a restricted budget.)