Originally Posted by Eskimo

If you are really trying to keep shipping costs reasonable, then you might want to carefully consider the possibility of sometimes using USPS Priority Mail with something other than the Flat Rate Boxes.

Those other flavors would include regular Priority Mail (which doesn't require a special box, but allows the use of PM boxes obtained from them at no direct cost to you). It would also include Priority Mail Regional Rate Boxes (which are special boxes, again, available from the USPS at no direct cost to you). I don't think that one can buy postage for Regional Rate Boxes at the post office, but I always buy my postage on-line at a discount anyway. It's easy, and I don't have to stand in line at the post office.

These are both Priority Mail, so they have the same "residential" advantages compared to UPS or FedEx, and the same "semi-trackability" that you are seeing with the Flat Rate Boxes. They are simply - in some cases - a lot less expensive then the Flat Rate Boxes.

As always, one has to consider whether the money one saves by getting the best price is worth the time one spent figuring it out! On occasion, I pay a bit more than absolutely necessary in postage because I want to get something out the door, and don't want to mess around trying to find or cobble together a "just right" box for it.