Money is a very big deal in this play. (Big surprise there, right? The plot revolves around a Venetian merchant who can't repay a loan to a hated moneylender.) In much of The Merchant of Venice, the characters' attitudes toward wealth, mercantilism, and usury (lending money with interest) function as a way to differentiate between Christians and Jews. The Christians in the play are portrayed as generous and even careless with their fortunes. The money-grubbing Shylock, on the other hand, is accused of caring more for his ducats than human relationships. At the same time, there's textual evidence to suggest that Shakespeare calls these stereotypes into question.
Although Shylock is made out to care more about money than human relationships, there's plenty of textual evidence to suggest that this is not true.
Bassanio may feel some affection (or even love) for Portia, but mostly he sees the rich heiress as a meal ticket who can get him out of debt.