"Champion blood lines" doesn't mean squat if you don't have the papers to prove it. Of course, papers themselves don't mean squat unless you are planning on breeding or showing.
JMO, but if she's using the "cost" of registering them as her reason for not doing it, then she's hiding something from you. (See any of the possible reasons that were listed above). The cost to register a litter is $25.00 plus $2.00 for puppy. Hardly cost prohibitive.
Fee Schedule
What she is selling you is a pet quality yorkie, no matter what the lineage she claims it has. For all you know, the pups could have been sired by the local Lothario. I'd walk away and look for another (reputable) breeder if she is trying to charge an arm and a leg for it.