It is kind of like gambling.
However, It is a risk some are willing to take when they want a breed that they cant find locally.
Last year I bought duck eggs on Ebay. This year chicken eggs.
I have gotten about 20-30% hatch rate on all of them. Which was 5 different batches from different people.
20% to 30% is at least something. Some folks don't even get a one to hatch out at all. I got last year a 5% rate hatch out and that was from a good breeder. 96 eggs total and 5 chicks hatched.