I've never heard of any of the authors on Baen though. They are not exactly Martin Amis or Dan Brown (depending upon your taste!). I doubt they see the earnings of the type of writers that the publishers are so keen to hang onto.
I agree with the maths behind the 20-30% discount being feasible.
And the idea of adverts as per the newest thread in this arena makes me shudder
IMHO
amjb