According to the conversion by weight, 1 Talent is about 25 kilograms of silver. In other words, the entire cash assets of Macedonia amount to 1500 kilograms of silver, and the debt amounts to 12500 kilograms of silver, leaving a deficit of 11000 kilograms of silver owed externally.
This amount is so large that selling him wouldn't cover the loss.
And as if his house was leaking and it was raining at night, Fortune herself didn't favor him.
Because his old father Philip II had died, and being quite young with little prestige, the city-states originally under Macedonian rule did not acknowledge him as King and declared independence.
In this internal and external trouble, Alexander staked everything he owned, launching foreign wars to reverse Macedonia's financial crisis, to plug the massive hole left by his dead father.
But fighting wars requires money.