On the surface, love and money are linked in The Merchant of Venice in that daughters are treated as property, to be hoarded and disbursed as their fathers see fit. Portia's marriage partner, for example, is to be chosen not by her but by the will of her dead father, as she is bound to marry the man who chooses the correct casket. The caskets themselves prove to be a riddle, connecting the value of precious and base metals to qualities of virtue. The one who chooses correctly will claim not only Portia but her family fortune.
Consequently, Portia is pursued by many suitors as though she were a treasure waiting to be claimed. Bassanio sails to Belmont not only for love but also with the hope of using her fortune to bail himself out of debt incurred through his profligate lifestyle. He wins Portia by correctly choosing the lead casket, on which the inscription reads, "Who chooseth me must give and hazard all he hath." Bassanio has already chanced all to get to Belmont, borrowing money from Shylock to fit himself and his retinue out in fancy clothes so that he may seem a worthy suitor. Since Bassanio's name is not good enough to secure a loan in his own right, he relies on the good credit of his friend, Antonio. In a sense, Bassanio has leveraged the love of his friend in order to purchase a love for himself that his own virtue may not justify.
To Portia's father and, by extension, to Shakespeare, Bassanio's recklessness in pursuit of love is the very quality that makes him deserve both love and treasure. Bassanio is willing to stake everything on a gamble, trusting his wisdom over outward appearance. In this sense, he is like an entrepreneur, whose risk taking is justified after the fact by his success. Antonio's faith in him is based not on his financial position but his character. In this sense, Antonio can almost be seen as an investor gambling on an entrepreneur based on the latter's character and vision.
Bassanio can best be contrasted with the characters who are guided by prudence and selfishness. Portia's previous suitors, wealthy men of good credit, could not see past the gold and silver of the first two caskets, and their lack of vision is met with failure. Shylock, in turn, is condemned for his lack of love and generosity. Just as he hoards his gold, so too does he shut away his daughter, Jessica. Lorenzo, acting life a thief in the night, steals both when Jessica escapes her father's house to elope with him, in the process stealing his gold. When Shylock exclaims, "My daughter! My ducats!" it appears he holds a daughter's love and his money in equal estimation.
In the end, Shylock is destroyed when he refuses to waive his claim to a pound of Antonio's flesh, despite being offered double the money he loaned. In this case, Shylock is clearly not acting in his financial best interest but rather to satisfy his desire for vengeance. It is clear that Shylock's anger is justified: Antonio and his friends have insulted him and lured away his daughter while stealing his gold. He has a claim to vengeance that is technically rightful just as his claim to Antonio's flesh is technically valid. His pursuit of this end without mercy, however, leads Portia to ruin him by technicalities. Ultimately, Shylock is punished for failing to show forgiveness and putting his selfishness ahead of a sense of humanity. To reinforce the point, Shylock is then shown mercy when his life his spared. Further, though by the letter of the law his property could be completely forfeit, it is instead generously directed to Jessica and Lorenzo as they make their start in life.