You cannot purchase any DF products with a domestic boarding pass. Since they don't charge you local sales tax, you have to show proof that you're taking the item out of the country.
I probably should have been more precise in my question. I have been to some Duty Free stores where they will charge you the correct taxes if you are not flying internationally and then I have been to other stores who cannot sell anything to a domestic boarding pass holder (aka they couldn't have the two price lists or calculate the additional taxes).
So I guess my real question is do you know if Hermes in SF is able to sell something to a domestic traveller and charge the appropriate taxes or if they are like some of the stores where they cannot sell anything at all to a domestic traveler.