If a product is defective, returning it with shipping cost for the vendor, would be perfectly normal. They are responsible for both product quality and shipping method, so if it is damaged in shipping that's the vendors problem: they should have packaged it better or used a better shipping service.
And yes, severe damage can occur in shipping due to all kinds of factors, sometimes packages arrived so mangled that even a flight data recorder would be malfunctional after the process
In any case, if the vendor isn't helpful, ebay does not resolve it properly either, it could be good if you paid with a credit card for that ebay transaction.
It depends on what credit card you have, but for example on mine i get a 4 month insurance on what i buy, pretty much against any form of damage, theft or loss unless intentional or by gross neglect.
So if i do buy something with that card and in breaks in transit, i could just ask them for a chargeback and they'd figure it out with ebay and ultimately the vendor etc, none of which is my problem unless i'm proven to be wrong and have caused the damage or loss myself.