I buy many hatching eggs.
If they wrap each egg individually, and then package individually, and pack well cushioned on all sides, and in between each egg, shipped pointy end down, the results were always much higher, even with shipping. I've sometimes had 90% hatch rates. However, if they just wrap each egg in a napkin, and put it into an egg carton and stick it in a box, your gonna lose eggs en route, and probably suffer some scrambling, because the eggs can move. Also, poorly packed eggs are subject to greater temperature fluctuation, which also lowers things. I've had 0 eggs of 6 hatch, or 1 of 18, or 22 of 24, it really depends.
This is the right way to get eggs if you want rare varieties, or special birds. If you have good incubating techniques (they are listed here at BYC - go read the Hatch Day is Today history, and learn a great deal), an accurate thermometer, and a way to measure humidity, you'll be fine. In the end, its up to you to make every viable egg hatch. I will definitely keep hatching, as for me it is more cost effective. We have many birds, but I prefer small amounts of each breed. Excepting my duck egg production flocks (which provide the hatching eggs for themselves) I rely on shipped eggs for my 4H kids.