I have a buddy wanting to trade for my jla collection but that's nearly a long box worth of books or more. Shipping would cost way more than the comics are probably worth even in flat rate boxes. Any one know of alternatives?
Best thing is probably USPS Media Mail which you can use for comics. It takes a few days longer to get there but is much cheaper than Priority Mail. Just for an example, it's around $10 to ship 20 pounds from East Coast to West Coast.
Have you looked into UPS Ground or FedEx Ground?
I haven't done a comparison in a few years, so all of their surcharges might have negated the savings that I recall they were over the post office for heavy things.
You cannot use media mail to ship comics. They contain advertising. You can lie and say its not comics. But media mail is subject to be opening by the post office. If they open it and find comics, you will be charged for the difference.
I've used media mail to mail comics quite a bit. Never had any problems and the postal workers have never said anything about it. As mentioned, they do tell you that they might inspect the contents of media mail labeled packages just because people will lie about what they are sending. If you know the weight and/or size of the box you shipping most sites (USPS,FedEx, UPS) offer estimates on shipping.