N80, send a letter to the store manager, CC to the regional manager, CC to the head office, directed tot he president. Denote the CC's ont he letter so each person knows who else is getting it. Let the pres know that their local store staffers are letting customers walk out with 500$ of stuff still setting in their isle, because they can't get another 30$ of stuff. I can almost guarantee you the pres will hand the matter off to an underling, who will either email you or contact the regional manager, who will then rough up the store manager.. probably the store or regional manager will contact you.
I know it's too late at this point for them to actually help you in this situation.. however .. in this economy.. i think people will jump and do a dance if they think/lknow they are loosing money.. You might as well see the song and dance for your troubles.
I've had to do this with napa and TSC before because lazy counter people won't get off their but to do anything.. and personally don't care if you are not going to make a purchase as they don't feel it hits thier personal bottom line..
soundguy