If the item you purchased arrived damaged or not as described, and you reported the issues to the seller or Reverb within 7 days of delivery, the seller would be responsible for the return shipping costs.
On a preference-based return, typically the buyer would be responsible for purchasing the return shipping label.
In most situations, sellers can purchase return shipping labels directly via Reverb. Once you approve the refund request to be returned, the option to purchase the return shipping label will appear on eligible orders.
For more information on refunds and returns, you can check out the Help Center articles below:
Refunds & Returns for Buyers
Refunds & Returns for Sellers
How Can I Request a Refund or Return?