If everyone involved says it's okay, then religious freedom applies. If the women wants to marry for love, then let her. But if she's okay with being sold for a $500 pig to someone, then religious freedom is in the 1st amendment of the US constitution. I say this as an atheist.
Regardless of whether or not the bride is okay with the dowry, it still objectifies women as a whole. People who take a dowry act as if women are merely objects of sexual desire, or worse, goods to be traded at will. By continuing with the dowry, we passively agree to allow this behavior to occur unchallenged.