What I fail to understand is why a buyer would spend anything at all on the chance that it's not fertile at all, and I fail to understand why a breeder, if the egg is good, would sell it at a discounted price when a few months in the incubator (zero additional effort) would make it worth significantly more the day it hatched? Either way, someone gets screwed, the buyer or the seller. If the breeder sells to the buyer an infertile egg, the breeder is better off (getting something for what would have been nothing), but then the buyer gets screwed. If the breeder sells a fertile egg for anything less than a hatchling price, he's shorting himself. The risks of shipping just add to the risk for the buyer; even if an egg starts out good, it could get damaged in shipping and never hatch.
We have handed a friend of ours an egg that was within days of hatching, they took it home, hatched and raised a beautiful tortoise (5 years ago), but it was given to him free with no expectations or guarantees of success.
I've hatched eggs from lizards, snakes, and turtles; it is one of the most rewarding aspects of reptile husbandry. Many years ago (when I was barely 21) I was riding my dirt bike way out in the boonies and came across a red ear slider nesting. I had never seen this before so I stopped and watched her for a while (mid-morning). I decided I wanted to try and incubate those eggs - not sure why exactly, but I had read an article on the topic earlier - so I returned with a bucket and a tablespoon and carefully dug them up and transported them home. I was totally ignorant on egg orientation and those eggs rolled around like marbles as I bounced them back home on that motorcycle.
The article I had read gave an incubation idea that I used: Styrofoam box, wire mesh grid inserted half-way to the top, water in the bottom third of container. Lay eggs on the grid (above the water line), place box in warm area, and wait for about...well, about forever. But about 2 months later, every single egg hatched and I suddenly had a dozen baby red ear sliders! It was fascinating, and got me hooked on breeding and hatching a variety of reptiles. It's incredibly exciting to see a tiny dinosaur-looking creature crack his way out of a shell that has lain perfectly still for weeks and weeks.
So I see the appeal of buying an egg, but in all honesty, with all that could go wrong in the whole process, I am surprised it is not heavily discounted in price. I would rather have the breeder set-up a live-cam on MY egg (still in his possession) and let me stream the blessed event for my viewing pleasure.