The secret code

The phone rang, and Mike answered it.  He told me that we were invited to a cookout tomorrow.
Me: Did you ask if we could bring something?
Mike: She said we didn't need to.
Me: I'm going to call her back and ask.
Mike: Why?  She already told me we didn't need to bring anything.
Me:  Yes, but you're a man.  You don't know the secret code of  women.
Mike:  What?
Me: It's kind of like when Abraham bought the field from the Hittite in Genesis 23.  He asked how much he would sell his cave for, so he could bury his wife in it.  The Hittite told him he could have the cave and the field it was in too. Abraham asked how much it was worth, and the Hittite told him it was probably worth 400 shekels of silver, but that Abraham could just have it for free.  Then Abraham paid him 400 shekels of silver and buried his wife in it.
Mike:  What does that have to do with the secret code of women?
Me:  Well, when I call her I'll say, "Are you sure I can't bring any food?" and she'll say that I don't need to bring anything, but then she'll start telling me the menu, and then I'll have to discern what's missing and offer to bring it.  Then she'll say yes, bring it.
Mike:  Really?
Me:  Probably.  I'll call the Hittite now.

So I call her, and I say, "Can I bring some food tomorrow?" and she says, "Oh, you don't have to.  We're just going to have hot dogs and hamburgers, and cole slaw, and chips."  I noticed she didn't mention any fruit, so I offered to bring watermelon, and she said that would be great.  We hung up, and Mike was looking at me.

Mike: What did she say?
Me:  She wants me to bring 400 shekels of silver.
Mike:  Women!