You lie!

Customer(on the phone): Do you have a book there that is a very big book of birds with pictures and you press a button and it plays the bird songs?
Me: Yes we do.
Customer: How much is it?
Me: $50.00
Customer: I saw it at another store in town for $25.00.
Me: Really? Maybe it wasn't the same book. This one is very large and has hundreds of pictures as well as the digital player for the bird calls.
Customer: I'm sure it's the same book. I'd like it for $25.00.
Me: I'm afraid that book is $50.00 - I won't be able to sell it for $25.00.
Customer: Fine - I'll get it at the other place.
Click
Not more than an hour later this same customer comes into the store - I knew from her voice right away.

Customer: Do you have a book of birds with pictures and you press a button and it plays the bird songs?
Me: Yes, it's right here.
Customer: How much is it?
Me: $50.00
Customer: Some other store in town has it for $25.00
Me: Is that so?
Customer: I'd like it for $25.00
Me: Well, it's $50.00. I can't sell it to you for $25.00.
Customer: It's somewhere else for $25.00.
Me: Where is that?
Customer: Somewhere else.
Me: Okay.
Customer: So can I have it for $25.00 then?
Me: No.
Customer: Fine I'll take it.

Why do people lie to us?