Shipping by UPS generally requires going through one of the "Mail Boxes, etc." type places.

Until just recently Mail Boxes Etc. charged a premium OVER what UPS charged. (However, I usually ship Priority Mail insured.)

When I was doing secondary sales, I usually bought NEW boxes for shipping. My time to buy boxes at Office Max, pack and deliver to the Post Office or to Mail Boxes Etc. is worth something, so I think it's only fair to pay something over the actual cost of the packaging and shipping.

No doubt there are SOME places overcharging for shipping & handling and the best advice is to confirm exact costs before buying or bidding.