
Generally a puppy that isn't KC registered simply can't be.
Either it is a close mating that isn't allowed, the parents are nto themselves registered, or have restrictions on their papers put on by their breeders to stop them being exploited.
The bitch is to young or old, had too many litters etc, so none of the reasons are good.
Occasionally breeders will sell registrable puppies without papers because they have some fault that makes them unshowable or unfit for breeding.
Those who claim they can sell you a pup registered for more money are either bluffing or will be giving false papers, after all it only costs £12 per puppy to register them.
It's the health testing, showing, vet care and rearing that cost the major money.