For me, the time saved using an i7 was enough to justify the price difference between the i5. And to be honest, I save more than 2 seconds editing/transcoding videos
Since I have a mild 4.4Ghz OC on my i7, I'm seeing rendering times around 5-10 minutes faster than an i5 at the same clock speed (Tested with and without Hyperthreading on my chip for a pseudo-i5).
For some of us, time = money. For others, they can wait and be happy with an i5
Don't get me wrong, though, the i5 is a great chip for almost any task you throw at it!