What you call a rock, madam, is the Mope Diamond and is not for sale at any price.
9 seconds sound clip from Batman (1966) - The Entrancing Dr. Cassandra (S3E25) TV Series.
You can hear this line at 00:09:15 in the Blu-ray version of the movie.
Quote context
[...]
- May I serve you today? Oh, just browsing, Dan.
- One does not browse at Spiffany's, madam. One either buys or one leaves.
- Shall I deck him, doc-y baby? He's trying to put us down.
- Cool it, love. We don't wanna blow the scene.
- Listen, Dan, tell me, how much are you asking for the big rock there?
- What you call a rock, madam, is the Mope Diamond and is not for sale at any price.
- Not for sale? Then I guess we'll just have to kipe it.
- You'll do no such thing, Dr. Cassandra.
- Oh, Batman. I see you've decided to take a crack at us. But I've got your number.
[...]