I can imagine any number of men saying "How ridiculous that I have to buy a diamond!" but without extending that thought process to marriage itself.
In that sense, buying a diamond is like graduating from college -- you've demonstrated a willingness to engage in possibly irrational behavior in furtherance of a widely revered symbol. This is not to say that college has no value, only that its value is often much less than the required investment. Just like marriage.
No problem -- if you aren't gay, you aren't required to have a gay marriage. But ask yourself if you want to deny that right to other people. That's quite a different thing -- it's not unlike saying, "I don't want black people marrying white people."
Before you reply saying, "But that's not a fair comparison -- black and white people are normal, but gay people are abnormal", consider that (a) it wasn't too long ago that black people were unfairly regarded as abnormal, and (b) there's no good evidence that being gay is abnormal, as that word is most commonly used.
Also, why not ask yourself the same question that judges are expected to ask themselves before making a ruling -- which is "Where's the harm?" How does the existence of gay marriage hurt you personally? Consider that gay couples are going to live together anyway (because being gay is not a crime) -- all that changes is that the rights and traditions of civil unions extend to those couples.
Clarification. I want LGBT equality including recognised marriages. But thinking about the bigger picture I don't see the point in state "you are in a relationship certificates" and think they should be abolished.
In that sense, buying a diamond is like graduating from college -- you've demonstrated a willingness to engage in possibly irrational behavior in furtherance of a widely revered symbol. This is not to say that college has no value, only that its value is often much less than the required investment. Just like marriage.