I feel the same as Pete ... the problem being, just like the stock market, what if you're wrong and prices never come back down to where you think they should be? Double whammy: You end up paying the same or more later, and ya missed out on fun during the period you waited.
In 2007 the Dow ranged between about 12k-14k, then the bust happened and it dropped to ~6,500. At that point you could've waited for "the bottom" to invest more, but it's been nearly all up since then and is now around 35k-36k.