What are the "injuries" in "The Cask of Amontillado"?

Poe was a perfectionist. It is hard to believe that he
would provide Montresor with such a strong motivation for refenge without giving some
clue to the "thousand injuries" he had suffered. Poe did not need to describe any of
these injuries in the opening of his story, which would have involved more exposition.
He knew he could demonstrate Fortunato's faults anywhere in the story. In fact, the
injurious behavior is so blatant that it can easily be overlooked by the
reader.

Fortunato is rich. Montresor is poor. Both men
apparently deal in luxury goods with millionaires. Here are a couple of significant
sentences in the third paragraph of the story:

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Few Italians have the true virtuoso spirit. For
the most part their enthusiasm is adopted to suit the time and opportunity to practise
imposture upon the British and Austrian
millionaires.

In that same
paragraph Montresor says:

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I was skilfull in the Italian vintages myself,
and bought largely whenever I
could.

This does not mean
that he bought largely whenever he could find good wines for sale but that he bought
largely whenever he could afford to. Both men bought art works,
jewels, antiques, and other luxury goods including fine wines to sell at a profit to
rich foreigners. Fortunato was rich and could afford to outbid Montresor continually. It
was in business deals that Montresor suffered most of his
injuries.

Note that Montresor does not consider himself an
Italian although he lives in Italy. He has a French name. He is not taking part in the
Italian carnival. He is wearing a French style cloak. He gives his victim French wine
twice when they are underground. His family may have lived in Italy for some time, but
he could still be considered an outsider by the aristocracy, and Fortunato might have
taken cruel pleasure in reminding him of his outsider status. There are a great many
human bones in the catacombs. This could be taken to show that the Montresors have lived
there for many centuries--but it is never stated that the bones belong to Montresor's
ancestors.

Fortunato is not interested in the Amontillado
because he wants to drink some of it or to show off his connoisseurship. He senses that
he might make a big profit. Montresor only bought one cask (a "pipe" containing 126
gallons), but Fortunato could afford to buy a whole shipload. First he must establish
that it is the true Amontillado. He doesn't want Montresor to go to Luchesi because
Luchesi is a competitor. For that matter, Montresor himself might become a competitor.
He twice tells Fortunato that he has his doubts about the authenticity of the
Amontillado. If Fortunato verifies that it is genuine, then Montresor might go back to
his source and buy some more. The suggestion in his saying, "I have my doubts" is that
he only bought one cask because he wasn't sure it was the real Amontillado. And
Montresor is well aware that Fortunato is thinking of beating him out of a good deal
once again if the wine is authentic. Montresor understands
Fortunato's ruthless character and hates him for it while using it against
him.