Returning damaged item to seller....

He should pay for shipping imo; however, be aware he’s more than likely out all the money, plus the money it’ll cost to get it shipped back and end up with a broken item unless he had the shipper pack and box because insurance won’t pay for damage.  
 

So maybe cut him some slack.

Does the price he charged mean he ate a large portion of the upfront shipping cost out to you, where he listed the shipping price as $40 thinking that’s all it would cost but was surprised at the FedEx for an additional $38.50 or damn near another $100 if he shipped USPS out of his pocket?  Or does he work for a company where he gets a discount on shipping?

The price you paid may not be indicative of shoddy packing.  The seller genuinely might have thought he did a good job.