Postage costs will be exact.
Fuck that. If you are going to do it right, you need the following:
Call Comics Unlimited and buy 1000 of their stiff cardboard comic box dividers Those are the white stiff cardboard 8 1/2 x 11 thingies with tabs that you see in every comic box in a store dividing the titles...takes about a week to get them to you and should cost around 150.00 for the thousand. You need two for each shipment, and when you "opposite" them the tabs match up nicely for shipping.
You need 2 backing boards in addition for the books themselves, and they run 5-8 bucks a hundred, and one bag for each comic, which is another 5.00 a hundred.
and newspaper...lots of newspaper.
Then go to the post office and take all the large PRIORITY MAIL TYVEK ENVELOPES they have. The big paper ones. Help ypurself, they are free. Go back once in a while and keep helping your self, make sure you have enough for your shipping.
Here's what I do... I take each book for shipment and put it in an individual bag. Then I take two of the backing boards and put them on either side of the books, however many there are. Then I wrap that package in newspaper. Then I take the stiff cardboard dividers and "opposite the tabs (one tab upper left, one tab lower right) and tape that securely with strapping tape. Then I take a tyvek Priority Mail envelope and TURN IT INSIDE OUT
When you turn the package you made with the books sideways, you'll find it slides in PERFECTLY TO THE BOTTOM. Then fold over the tyvek and tape the two sides up. A perfect indestructible white package, tight and sweet.
For 1-5 books, MEDIA MAIL costs 1.84 to ship. if its just one book in the order, ship it first class, its $1.34.
Insuranc is optional, as is proof of delivery, make sure you state that (1.00 for insurance under $50, delivery confirmation is an extra .35
Make sure you point that little detail out too, that without insurance or POD you can't "guarantee" delivery. While it's not a big deal, and the mail is rarely lost (I've lost ONE media mail uninsured package in the 10 years Ive been doing this) there are many unscrupulous buyers out there who will say they never rec'd the package and demand a refund, or worse. This little caveat will protect you from the assholes.
The best formula to use with this system is...$4.00 one book, 5.00 2-10 books, insurance (optional) 1.00 up to $50. 2.00 over that, and 50 cents for POD. That will cover all your costs without having anything go out of pocket. remember, your listing fees and commissions will run you .45 on every dollar book you sell...this will help keep all the fees and costs paid, and wont gouge the buyer at the same time, because the package is so slick when it arrives like this