"The Siege of Tyre was orchestrated by Alexander the Great in 332 BC during his campaigns against the Persians. The Macedonian army was unable to capture the city, which was a strategic coastal base on the Mediterranean Sea, through conventional means because it was on an island and had walls right up to the sea. Alexander responded to this problem by first blockading and besieging Tyre for seven months, and then by building a causeway that allowed him to breach the fortifications.
It is said that Alexander was so enraged at the Tyrians' defence of their city and the loss of his men that he destroyed half the city. According to Arrian, 8,000 Tyrian civilians were massacred after the city fell. Alexander granted pardon to all who had sought sanctuary (safety in the temple), including Azemilcus and his family, as well as many nobles. 30,000 residents and foreigners, mainly women and children, were sold into slavery. ... According to Quintus Curtius Rufus 6,000 fighting men were killed within the city and 2,000 Tyrians were crucified on the beach. The others, some 30,000 people, were sold into slavery. The severity of reprisals reflected the length of the siege and Alexander's response to the Tyrians having executed some of his soldiers on the walls, in sight of the attackers." This is the justification given by Wikipedia for Alexander's behavior. Let me stress that Alexander was attaching Tyre not viceversa!
From http://factsanddetails.com/world/cat56/sub366/item2036.html "The victory over Tyre added Lebanon as well as Palestine, Syria and Egypt to Alexander's empire.Alexander was reportedly so enraged by the loss of time and men used to capture Tyre that he destroyed half the city, and rounded up its residents, who were either massacred or sold into slavery. Seven thousand people were slaughtered after the capture, 2,000 young men were crucified and 30,000 people were sold into slavery." Ecco come finanziava la sua guerra Alessandro. Faceva cassa ad ogni città conquistata.
That is, it is clear that the financial support for Alexander's war that of selling people for slavery.