Amontillado is a type of sherry made in Spain. It is prized by connoisseurs. In Edgar Allan Poe's story, the protagonist Montresor claims to have just received a "pipe" of what is represented as Amontillado but wants some expert to taste it and tell him whether it is genuine. A pipe contains 126 gallons. Montresor tells Fortunato that he bought it at a bargain price. This is the crucial part of Montresor's finely honed story:
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."
Montresor does not say this in so many words, but his urgency to get the wine tested that night is intended to suggest that he would like to buy more and can't do so unless he is sure it is genuine Amontillado. The fact that Montresor has supposedly bought such a large quantity and would like to buy more shows he is not interested in the wine for personal consumption but as an investment. Amontillado in an oak barrel only improves with age. Aging is one of the things that make it so desirable in the first place.
Fortunato only agrees to go to Montresor's palazzo because he too is interested in buying some at a bargain price. Montresor wants to lure him to his underground catacombs immediately to keep Fortunato from asking questions around town and finding out that there is no recently arrived cargo of Amontillado aboard a ship from Barcelona--the only place the Amontillado could have come from. Montresor uses another connoisseur named Luchesi to force Fortunato to come with him immediately. Fortunato does not want Luchesi hearing about this bargain-priced Amontillado.
Of course, the Amontillado does not exist. It is only used to bait a trap. Montresor fully intends to kill Fortunato once he gets him underground. He has no intention of going to Luchesi. Montresor is a daring man. He is taking many chances at this crucial point. He could be recognized as being Fortunato's companion and come under suspicion after Fortunato disappears. Montresor wants to be above suspicion.