I am Hybridizing but have not named or introduced anything yet as just getting started so I would not want to be included in a list yet but later I would. I think it should be only of those currently introducing and registering their daylilies, That would include any seedlings purchased that they felt worthy as they are theirs once they bought them.
I have purchased seed from Ann and she sells some amazing crosses that I hope one day to see something from. Takes so long here. Any beauties and good plants I would either test elsewhere or use as bridge plants onto hardy northern plants.
You ask why Gaskin seedlings go for so much. Because the Gaskins have a keen eye for what will become an awesome plant worthy of registration and envied by many. Take a look on the AHS under Gaskins and see what comes up. WOW. People in the business have come to trust and repect the knowledge that has been put into those crosses.