I got engaged recently, and my fiance and I have examined a lot of "things" surrounding engagement and marriage which seem absolutely ridiculous.
For instance, as you stated, the diamond (or otherwise super-expensive) ring. Why is it a thing that a man is supposed to give up months' worth of his salary to get a piece of jewelry? That seems horrible to me; and crazy on the woman's part to expect that level of expense. Last Valentine's Day, I was driving with the radio on, and an advertisement came on. It was trying to sell a $5,000 dollar engagement ring on a payment plan, saying, "You'll have it paid off in 5 years!!" as if that was a wonderful deal. Meanwhile, my fiance and I bought a pair of nice $25 dollar wedding bands--and that's all we want!
In a similar vein, where did the super-expensive wedding dress come from? I cannot imagine spending thousands of dollars on a dress I only plan to wear once. In my case, I bought a nice-looking white dress with my own money, very cheaply. It isn't a wedding dress at all (which is why it was so cheap), it just looks like one.
Then there's the idea that the wedding is a bride's "big day," and should be all about her. I think the wedding day is the least important day of all for a married couple--it's all the days after that matter, the days where two people have to make their relationship actually work. If the wedding day is for anybody, it ought to be for the families of the two people. It seems strange that our society treats weddings as a flamboyant display meant to please the bride. As a soon-to-be bride myself, I can't imagine anything more self-centered and ridiculous.
Some other "things" my fiance and I have encountered during our relationship include:
-The man is supposed to have a car to drive the woman around in, and, the man is supposed to pay for the dates and outings. (REALITY: I have a car, he doesn't; and I make more money--so I do the driving, and I pay for dates more often.)
-Women with body hair are gross, and men don't find them attractive. (REALITY: I haven't shaved in years. My fiance likes to play with my armpit hair.)