I agree with Randy, management can make a big difference in a birds appearance but genetics determines most of it.
In any given hatch or litter of anything, no matter who its from, even elite breeder, I would dare say as an example... out of a hatch of say 10 gosling's you might get a couple that are show quality.
Theres an old saying in show circles...champion x champion = chumpion, so when people say that the offspring are out of show birds and they're show quality it basically mean nothing. Theres just no guarantee.
Granted some breeders through years of selective breeding and culling have refined the breeding stock they're working with and can pretty much stamp out the same type time and time again but I wouldn't pay a premium price for so call "show quality" babies because you never know what they're going to look like as adults. Thats why alot of breeders don't sell gosling's until Fall because they grow them out to see how they turn out and keep the best and sell the rest. You really have to breed your own keepers and then follow through with good management.
Heres another factor...Sebastopols can looking pretty ratty during late winter - the breeding season, due to wear and tear on their long feathers.
Many lose quite a few and just aren't as pretty vs. after they molt late summer/fall and get their new feathers in. They're in their prime feather Fall though about mid winter. Some will blow alot of their feathers and some will retain them pretty good but all of them suffer from wear and tear to those long flowing feathers. You will also have white feathers everywhere when they start shedding.
Randy what other bloodlines are your Sebastopols from?