Question

Why does Gladwell use the word "bargain" instead of "agreement" or "deal"?

Answer 1

Because Bargain involves the process when a buyer ask for lowering the price of a product, and sustain a negotiation process with the seller.

Agreement or deal, is about the end process, the result of the bargain.

Answer 2

bargain: an agreement between two or more parties as to what each party will do for the other.