I had one order of eggs arrive in paper towels, in a carton, padded with wadded paper. 15 eggs, rattling around in the carton, 3 were broken. It was my 1st time getting shipped eggs, I didn't know about detached air cells, so I don't know whether they were or not. Only 1 chick hatched, my $29 chicken.
On cost of shipping, in addition to gas to the P.O., bubble wrap (or whatever), and postage, there's cost of delivery confirmation, and though it isn't part of shipping, PayPal charges sellers a fee, which is usually recovered from the S&H charges.
If you package like I and many others do, it may take around an hour or more to pack this eggs.
I charge actual postage, plus enough to cover gas, DC, PayPal, and any packing materials I have to buy, if I've run out materials from shipments I've gotten. I haven't charged for my time, but have considered doing so, and I might, in the future.