It is not good for the OP or anyone producing heritage birds, or any birds for that matter to sell them for less than it takes to produce them. Given the price of Marans last year I am sure that the cost of producing chicks far exceeds OP expectations. OP if you are looking for inexpensive birds to have in your coop for some eggs I suggest you head off to your hatchery of choice and do that. If you are thinking about getting into these birds and have some to hatch and ultimately sell it is not good for you to have cheap birds available to you.
A lot of breeders go to a lot of trouble and expense to produce a good product and someone wants them to sell them for under production cost. It doesn't make any sense.
One of the things I have discovered is that if you show a genuine interest in a breed, go to a few shows, and convince a breeder that you might actually do something with some birds, many times they will give a person a great deal. I have given eggs and chicks to folks like that. If folks simply ask me to sell birds for cheap, because they simply want some of my birds, frankly the price goes up.