How does Montresor get Fortunato to come to his palazzo?

I said to him—“My dear Fortunato, you are luckily met. How remarkably well you are looking to-day. But I have received a pipe of what passes for Amontillado, and I have my doubts.”

“How?” said he. “Amontillado, A pipe? Impossible! And in the middle of the carnival!”

“I have my doubts,” I replied; “and I was silly enough to pay the full Amontillado price without consulting you in the matter. You were not to be found, and I was fearful of losing a bargain....As you are engaged, I am on my way to Luchesi. If any one has a critical turn it is he. He will tell me—”

Both men refer to the cask as a "pipe," which is a barrel containing 126 gallons, or some 500 quart bottles. Neither Montresor nor Fortunato would want that much sherry for private consumption. The "bargain" in this purely fictitious Amontillado is the bait in the trap.

Montresor pretends to be in a hurry, which is why he uses the word "But," as if to say, "But I can't stop to talk now because I am in a hurry." Why should he be in a hurry to get someone to sample his wine? Because he got a bargain and would like to buy more before word gets out--if only he could be sure it is genuine. What interests Fortunato, as Montresor well knows, is the "bargain." Fortunato does not want to do Montresor a favor by sampling his wine. He is having a good time. He is inadequately dressed. He has a bad cold. But he can't put Montresor off for a day or even an hour because Montresor says he is on his way to Luchesi, who is obviously another connoisseur and another man who would be interested in a shipment of gourmet sherry being offered at a bargain. Fortunato does not need to sample Montresor's (nonexistent) wine. He could easily find a Spanish ship that brought the cargo of Amontillado to Venice. He could taste the wine aboard the ship and make a deal with the captain or purser immediately, thereby cutting Montresor out and committing another of his "thousand injuries." But if he doesn't go home with Montresor, Montresor will go to Luchesi; and then Fortunato would find himself competing with another buyer and  bidding the price up. Fortunato, as Montresor knows, since he knows his man, is already planning to taste the wine and say it is only ordinary sherry, whether it is or not. That would eliminate Montresor from the competition as well as Luchesi.

Montresor knows it is not enough to say he has a cask of Amontillado in his underground vaults. He has to make it a matter of urgency that it be sampled and judged by an expert that night. It is urgent because the wine is only a bargain as long as nobody else knows about it. And nobody else knows about it yet because everybody, including Fortunato, is drunk and neglecting business during the carnival.

The whole story is based on Montresor's problem of enticing Fortunato to his palazzo. Montresor manages to remain unnoticed because Fortunato is so boisterous and so conspicuous in his jester's costume and his cap with ringing bells. Montresor in his black cloak and black silk mask is like a shadow. No one will remember seeing him, although everyone will remember seeing Fortunato. Besides, Montresor has gone to great pains to make everyone, including Fortunato, believe that they are the very best of friends. When Fortunato disappears, it will be natural to suspect foul play--but no one will suspect Montresor. He has thought of everything.