Quality, knowledge and the price people are willing to pay. Hatchery cuckoos probably do sell for $4 a piece but do not lay dark eggs from what a number of folks have told me, although I have no actual experience with them. Typically hatchery stock is bred for egg production and with Marans, the egg color is often a very challenging thing to achieve.
So many folks are selling them at this point because they can fetch high prices. Sadly there are many poorly bred birds out there or, folks get them and instantly start selling them, not having any idea about breeding, or even what makes a quality bird.
Do your research. Typically the established breeders (those who have created numerous generations) sell their eggs for $60-$75 a dozen. Sometimes the eggs on
ebay are ok, but often they are NOT. Waiting lists can be a year or more from a really good breeder. Sometimes less for sure. Don't just hop in, learn and ask the breeder a lot of questions. Look for an experienced breeder who will answer all your questions openly. Ask for an egg sample. Ask what number the eggs are on the scale. Ask what flaws their birds have. I have researched and done all this and still gotten very light eggs from folks who assured me their eggs meet the standard.
There is the Marans Chicken Club or Marans breeders of America online as a resource.
They are a wonderful wonderful breed, but are a work in progress continually due to the challenge of achieving the dark egg color.
Best of luck!
Good luck!
Edited to add: JUST BECAUSE THEY ARE EXPENSIVE DOES NOT MEAN THEY ARE QUALITY.
