In "The Cask of Amontillado," who is Luchesi and what purpose does he serve?

I have previously suggested that both Montresor and
Fortunato are aristocrats but earn their livings by dealing in expensive goods such as
paintings, antiques, jewelry (gemmary), and probably gourmet wines. This is implied in
the third paragraph of the story which includes these
sentences:

readability="12">

Few Italians have the true virtuoso spirit. For
the most part their enthusiasm is adopted to suit the time and opportunity to practice
imposture upon the British and Austrian millionaires. In painting and gemmary,
Fortunato, like his countrymen, was a quack, but in the matter of old wines he was
sincere.

When Montresor tells
Fortunato that he has purchased a cask of Amontillado at a bargain price, Fortunato is
naturally interested in buying some for himself. That is the main reason he wants to
sample it. Montresor repeats that he has doubts about its genuineness. Obviously a ship
carrying a whole cargo of the wine has recently arrived in Venice. Fortunato normally
would have heard about it, but this is the height of the carnival and people have been
neglecting business.

Fortunato would not need to sample
Montresor’s wine. He could say he was too busy and would do it later. He would have no
trouble finding a newly arrived Spanish ship loaded with big pipes of wine (each
containing 126 gallons). That is why Montresor tells
him

“As you
are engaged, I am on my way to
Luchesi.”

This is very good!
He says, “I am on my way.” Time is of the essence. Luchesi must be another man who deals
in luxury goods, another competitor. Fortunato does not want him to hear a word about
the Amontillado. He accompanies Montresor to his vaults—not out of friendship or to show
off his knowledge of wines, and certainly not to drink a glass of wine in a dank
catacomb when he has a cold and is inadequately clothed--but in order to keep him from
going to Luchesi. If Luchesi knew about the shipload of wine, he would find it quickly
enough. Everybody on the waterfront would know about a newly arrived Spanish ship. Then
Fortunato would have to be competing with the other aristocrat-connoisseur-businessman
in bidding on the cargo. Both of them could sample the Amontillado (if it existed)
aboard the ship to make sure it is genuine. There would be no need for either of them to
taste Montresor’s wine.

Fortunato can afford to buy the
whole shipload. Luchesi is probably able to do the same. Poor Montresor would be left
with his one cask of Amontillado for whatever small profit he could make selling it in
bottles. But Montresor knows Fortunato’s mind. Fortunato is already planning to taste
the wine and tell him it is only ordinary sherry. Then, assuming it was genuine,
Fortunato would go to find the captain of the Spanish ship. We can assume that tricks
like these are among the “thousand injuries” Montresor has suffered over the
years.

Why does he maintain relations with Fortunato?
Fortunato is rich. Montresor may need to borrow money from him or to go into joint
ventures with him if it is a question of buying an expensive item, such as an oil
painting, for resale.