Cost of fuel directly proportional to an "Impulse buy"?

I was talking the other day with a friend about how it's funny how impulse buys have changed over the years. It used to be $19.95 was the magic price point. Anything over that was "hmmm... I need to think about that... maybe next week". Now it seems like the latest gadgets are $50 or $100 and people say, "That's reasonable".

So my new theory is: "An Impulse Buy is directly related to the cost of a tank of fuel."

I hope that means that fuel prices don't rise to iPhone levels anytime soon! Or do i?