One thing to keep in mind is that I think I have an obligation to the people on down the line.
My birds came from a breeder with a very good reputation. If I sell my culls as pets, what is to stop my buyer from representing those birds as top show quality and using the well known breeder's name to sell hatching eggs?
Then the buyer of the eggs spends a great deal of money to buy eggs and ship them and puts all the effort of incubating them, only to get pet quality hatchlings, maybe that have inherited a disqualification from the pet quality parent.
It's a bit different at a poultry auction, because the birds can be sold without their "pedigrees" (the name of their lines or breeder), or even sold without the breed being identified. At that point, they are simply birds, what you see is what you get.