Tothemoon, I bubble wrap each egg separately, putting in a regular box (not an egg carton) which is then cushioned and set in a larger box. These are not the prepaid priority boxes but we use the large boxes that can be ordered through USPS as the standard mailing box. Our mailing costs can often be higher than the prepaid boxes but we find that they arrive in better shape, so it's well worth the extra time, packing materials and shipping costs. Occasionally with a large order, we will use an even larger outside box.
It's proven a much better way to ship, more labor intensive, but better end results.
I also find that when I buy eggs, if folks will ship this way, I get much less damage on the eggs...
For how I roll up the bubble wrap, please see the display by dipsy doodle doo.
Hope this helps and great luck