Any seller who puts this in an ad knows that the shipping companies will not deal with a recipient who claims damage. If a recipient claims damage they will schedule a pickup to send it back to the shipper and that's all they will do for a recipient.
The seller wants you to bet the entire cost of the equipment on UPS or FedEx getting it to you undamaged, a bet I wouldn't take.
All you can do is not buy from these sellers. Audiogon should make them take that stipulation out of their ads.