As for the JD Sinatra: Remember it's the same whiskey as the regular black label (actually as all JD except the new rye); same mash bill, distillation, filtration, aging etc.; they just select the barrel. I'm sure there are differences, but differences between $25 and $200? Hmm...
As for Pappy: A legend in danger of becoming a myth. I once was able to do a favor for a friend's business associate and in return found myself invited to a social function way above my usual socio-economic circles; in plain English, I got to hobnob with the rich. There I had the chance to drink Pappy. An excellent bourbon, but that's it. Worth the money, the hype, the waiting lists? Not so much.
This blog has a nice recipe for a substitute Pappy made from two iterations of Weller, from the same distillery that makes Pappy:
Poor Mans Pappy - Bourbonr Blog