I have shipped both glass, and also vintage electronics including turntables, tube (valve) components and the like for about 10 years now. I have shipped all over the world from Seattle. I have shipped items successfully weighing anywhere from 1 lb to 40 lbs using this method. I have never double boxed an item and have used only bubble wrap and peanuts. I have always used large bubble wrap, never the stuff with the small ones.
The US Post Office also views paper as an unsatisfactory packing material and will generally not pay claims unless the item is double boxed, and done very well. The problem with paper is that it compresses very easily allowing for motion inside the box during transport. I even looked at a type of packing paper that is available to me that is coated on one side with a thin layer of a rubber like material to help it hold it's shape and decided that it too would compress during shipping.
My experience with double boxing is that it increases the cost of shipping an item, and in turn decreases the amount one can get for product, as the end user generally sees the whole thing as one purchase, and is willing to spend less on product if the items shipping cost is higher. If their budget total, for example, is $100, they really don't care if it is $90 for the item and $10 for shipping, or if it is $80 for the item and $20 for shipping. I have never tried to make money on shipping, but I really like getting $90 for my item instead of $80.
The increased use of US Postal flat rate boxes for shipping is driven by the buyers desire to ship inexpensively coupled with the sellers desire to get more for their product. These two desire are diametrically opposed to each other. I only charge a fee on ebay for packing for large items such as electronics and always divulge that in large text in the auction listing itself. In those cases I charge as much as $15 which buyers are willing to pay. I do know that when I charge the fee for packing materials, it is generally coming off of the bid price of the item I am selling. It is part of the cost of doing business through the internet.
My shipping method is to wrap the item well in large bubble wrap. Generally I wrap it around 3 inches thick around the object to be shipped. I then put a good layer of peanuts in the bottom of the box (2-3 inches deep). I lay the item on top of the peanuts and then put the four flaps straight up. I then cover the item with peanuts assuring that there is a good quantity between the object and the sides of the box. In many cases I will flex the box sides out one at a time to allow for a few more peanuts to fall in the space. I fill the box to about 1-2 inches over what will be the top edge of the box, and then compress the contents using the flaps that I am going to tape closed. In most cases the top of the box will be bowed upwards slightly from the compression, as I pack very tight.
I typically use Post Office supplied boxes for mailing most glass, and I custom buy boxes for electronics which generally allow for 2-4 inches of space around an item in all directions. The US Post Office boxes are not the thickest boxes in the world by any means. but even their 12x12x8 inch box weighs in at just under 1 lb. (.45 kg). The empty box would cost just under $5 to ship in the US.
I have found, and I have never lost an item to damage by any shipper (here is where I knock on wood and hope that I have not jinxed myself by saying this), that compressing the peanuts to make sure there is absolutely no movement of the object due to the peanuts being too loose is the key. I generally allow at least 2 inches or more of space between the bubble wrap and the box. This will increase a little depending on the weight of the object I am shipping.
Most damage I have seen in receiving items is not from overly rough handling during transport, but from "under packing" the item allowing for motion of the object inside the box during shipping. If the item can move at all, it will during shipping. It will either compress paper, if that is used, or it will "rearrange" the peanuts and make it's way to the box, and eventually suffer damage from the smallest impact. The key is in the compression of the box with the peanuts inside. It needs to take some effort to make it square up to tape.
I have shipped in excess of 1200 items successfully using this method.
Craig