If you ever ship books, CDs, DVDs, sheet music, etc. check to see if it qualifies for USPS Media Mail. In most post offices they just ask the standard “is there anything dangerous” question, and offer you the “cheapest” shipping method. Usually you need to request Media Mail, and usually it is about half the price of the next cheapest option that they originally quoted you. Your package is subject to inspection, and if you get caught violating the guidelines, you will be out the media mail postage and it will be sent back to you to ship again. I imagine they offer this so that they capture high-volume business from people who know about it like Amazon, businesses, etc., but they don’t advertise it because they loose too much money on it if the general public uses it (even legitimately.) Also, don’t look for this option in the self-service shipping kiosk in the USPS lobby, because they don’t trust the general public to follow the rules, (and somehow think that making you talk to a clerk and answer them directly will prevent abuse.) So if you are like me, and hard-pressed to find time to go to the post office during normal hours, it will be a cost vs. convenience trade-off. I hope this saves you a little bit of money the next time you ship something you have sold on Amazon, E-Bay, etc.
I found more evidence to support my theory that the USPS gives preference to bulk mailers. I knew thay gave discounts, but this is crazy. They give companies steep discounts to send out tons of junk mail like this mailing I got yesterday. Apparently bulk mailers only have to pay 19 cents to send a letter, not a post card, but an envelope, a form and a return envelope enclosed, while the rest of us are stuck paying 44 cents for a first class letter. At least the return envelope was no postage necessary. I wonder what they pay to receive it back.