I have shipped eggs, but within a day or so after laying. One was infertile, two started hatching, but only one made it out all the way and grew up just fine. I have read about others who have also successfully shipped eggs shortly after laying. I filled half a delicup with moist perlite or vermiculite (can't remember which it was) put the eggs in with a mark on the top of them, filled the rest of the cup up, and put the lid on with a tiny pinhole in the top. I made sure the shipping box was really well padded and it was lined with styrofoam. The temps were good so I didn't use a heat pack. Because we weren't sure if it would work (I didn't know of anyone doing it successfully at the time) we didn't want to pay for expensive UPS/Fedex shipping and went with USPS. I used priority shipping because express wouldn't get there overnight anyways (and they got there in two days just as if I sent them through express but for 3X less money.) The eggs turned out just fine. His 3 eggs started hatching 2 months earlier than mine (we think the shipping stopped the eggs from going into diapause, where mine went into diapause and I broke it by gradually warming the temps up.)
I wouldn't ever ship out eggs past 1-2 weeks after being laid. If I were to pay for eggs, it wouldn't be very much, and I would never pay for eggs that are 5 months into incubation. If someone wanted to go ahead and send them to me as an experiment, I would do it and pay for the shipping, but nothing more.