I once brought a Music Reference RM5 mkII preamp with me on a vacation from Philly to LA and then drove up the coast to SF to personally deliver it. The buyer met me in the lobby of my hotel room and then when he showed up, he asked me about a discount (after the price was long ago negotiated), since he didn't have the opportunity to audition it.
I said, "you're kidding, right? I schlepped this thing all the way here, and drove it up the coast to bring it to you; I have no problem bringing it back home and keeping it." At that point, he paid the price that we agreed upon.