That is a touch subject that may or may not ruffle some feathers. In my opinion I don't think that's the right mind set you should be in. Its one thing when there's complications and it's unlikely that the animal is going to survive, it happens. Line breeding is a less ugly word for inbreeding, but another entirely when you want to kill them off just because they are normals. I know for a fact that there are rodent breeders who breed with the intention of their animals being pets and not used for feeders.
That's just me, unless you are breeding 4+ gene males to 2+ gene females there's going to be a good chance for normals in your clutch. A $20 normal might not mean much to you but might mean the world to someone else.