Time Waster Thursday

We have a family that's been coming into our store for a long, long time. Unfortunately two of the teen daughters have this bad habit of tying up employees so that they cannot help other people. These girls only want you to drag out EVERY SINGLE THING in the display cases (not picky which display case either, if it's locked away then they want to see it!) These girls will never buy anything, it's like a hobby for them to waste our time.
Finally, I had enough of it. While helping the mom, the daughters will constantly interrupt our transaction with, "I want to see that ring/camera/etc." to the point that I got pissed off. How many times does one person act like a rude ass?? Every time? So after multiple time-wasting sessions of showing them everything for 30, 45 minutes, I finally put the quash on it. The next time one of the daughters started interrupting my transaction with, "I want to see that", I asked her, "Are you going to buy anything today?" She laughed at me and said no. I told her (gently) that when she was serious about buying, to come see me and I'll be glad to take things out, but when I have other people waiting to be helped I can't do that. She has not asked to see anything since then. (You can see it through the glass, you don't need to pet it if you just want to waste time!) Today her sister and boyfriend (who lets their 14 year old daughter date, let along date a guy who's not even a teen any more?) spent half an hour looking at weapons, while a legitimate customer who DID want to buy something, stood by waiting. I was so mad. I was busy at the other counter or I would have just gone to help the REAL customer and told LookieLoo that I'd be back over later when they wanted to buy something!