Excusing childish behavior by calling it rational doesn't make it less childish. Relationships or hook-ups might _start_ on factors like that, but they don't survive if that's what constitutes the substance of it.

And if the _symbol_ of your supposedly permanent commitment is a diamond, that says something very cynical about that marriage.

I'm sure there are good marriages with diamond rings involved. I'm pretty sure those marriages aren't successful because of that, but rather in spite of it.