In 2017, a single violin bow sold at auction for $690,000. You can buy a beginner's bow for less than $50, but a top-rate professional bow can often cost thousands of dollars. A bow like this is completely handcrafted by skilled artisans. And just one can take an entire week to make. Even the most subtle differences in the way a bow is made will change how well it plays. So why would someone pay so much for a bow? And what makes it so expensive?