As someone who
actually breeds Seramas...
They can be a bit tricky to hatch in an incubator. Usually broody hens do better with them. Chicks may need their crumble crushed even finer. The breeder I got mine from mixes crushed mealworms into the feed as well. I've offered boiled egg finely chopped and dried mealworms to chicks.
Pricing is going to be determined by supply and demand as well as the quality of your birds and the variety of color patterns you can get from them. I sell pairs for $50. Some very good-looking pairs may go for more. I rarely sell chicks as most people will kill them trying to raise them. If you're looking to make a killing with them, look somewhere else. Seramas are highly seasonal layers and may take breaks for months at a time.
There is absolutely nothing wrong with line-breeding. Keep in mind when pairing closely related birds, both defects and good traits will be magnified in the offspring. I usually breed in pairs or trios. I'll be trying a small, mixed flock for the first time later this year. In general males don't over-breed hens and are very gentle.
@Faraday40 breeds Seramas and may have some more helpful tidbits to share.