I heard a story about a woman who only wanted a plain band as her engagement ring. The engagement lasted about a year. The wedding was planned, the guests invited, and only a couple of weeks remained. The groom decides that he doesn't love his bride as much as he should love the woman he wants to marry. He calls the wedding off and she is left out in the cold.
The groom said that he would pay any remaining balances for the wedding costs, but he would not marry her. So... one friend told me that this is why engagaement rings should cost the man a lot of money: because most men would seriously weigh spending so much on a ring for a woman they could not see spending forever with. And at least if he pulls a stunt like this one, she's got something pricy to pawn