The movie "Seven Pounds": what does "pounds" mean here?

This is apparently alluding to Shakespeares "Merchant of Venice", were a debtor owes a pound of flesh - and since the protagonist in the movie is "paying back" seven lives, it's seven pounds.

According to Wikipedia, Will Smith confirmed the connection:

Will Smith is reported to have confirmed that the title refers to Shakespeare's The Merchant of Venice, in which a debtor must pay a pound of flesh

While, being a Shakespeare fan, that was basically the first thing I thought of, I don't think it makes a lot of sense, since nothing in the circumstances of the debt in the play is even remotely parallel to what happens in the movie. But if the main actor/producer confirms it, then that's probably it.