One popular snowclone is to say that "If I had an X for every time that I've heard Y, I'd have enough X's to be/do Z." Usually these are ridiculous exaggerations once broken down. For example, "If I had a penny for every time you said you'd clean the dishes later, I'd be a billionaire." Totally untrue and impossible.
In one of my classes today someone said, "If I had a dollar for every time I heard X, I could buy us all beer tonight. But I don't, so you will all have to buy your own." This managed to be actually funny. On closer inspection I think it's because what he described is a legitimately plausible scenario, especially coming from a snowclone in which we are habituated to hyperbole. There were about twenty people in the class. It is reasonable for him to have heard this particular argument thirty or so times, and that probably adds up to enough cash to get us all tipsy on tall cans of PBR.
This plausability humor runs directly contra to the explanation of humor as exaggeration, which claims 400k+ Google hits. The website My Life is Average also is contra to the exaggeration hypothesis, humorously parodying the excesses of FML. It seems that the balance of what is funny at a given moment really does wax and wane like a sine wave.