I know that as booksellers we are always looking for ways to minimize our shipping costs, particularly since we get fixed reimbursements from the marketplaces, but the shipping of rare and/or collectible books is not the place to scrimp.  The buyers of these books are very interested in maintaining the conditions of the books they buy and getting one in the mail that is totally unprotected is not their idea of quality service.

If you sell a rare or collectible book, the minimum protection you should provide are cardboard over the covers and a bubble pack envelope.  What you want to avoid is any new damage to the book while it is in transit to your customer.   If you ship it unprotected, not only
do you risk it being rejected and returned by your customer, you also risk negative feedback owing to a perceived negligence on your part by the customer.

A little care and attention to detail can go a long way when dealing with book collectors and the books they buy from you.