If I had more money for app fees (& GRE & transcript fees), I would've applied to a few more, although they would've been top 25 schools, or at least fully funded programs. My rationale was that if I could get into a top fully-funded program, I'd get into one of the ones I applied to -- and if I couldn't get into one of my top 4 choices, then I probably wouldn't get into one of my top 10 choices either, and if I wasn't accepted into a fully-funded top-tier program then earning a PhD wasn't worth it anyway. And at the time spending another $500 on apps seemed futile.
...But now that it's results time and it's hitting me that luck actually is a pretty big determining factor, I wish I would've applied to a few more schools. At least one of my schools is ranked lower, depending on which rankings you're looking at, and is fully funded (USC) so I'm crossing my fingers for USC (& still for Columbia and/or Princeton!). And deciding tomorrow on U of Oregon and/or Claremont.