I think the post-Katrina gasoline spike has changed me for good. I finally reached my pain point (I get reimbursed for business mileage, but $500/month for gas between my wife and I was still ridiculous).
When I want something, I now almost always think what's the car cost? The number I use is 30c. Gas today is 12c. Car depreciation is normally about 15-18c. Oil and tires is 1-2c. It's 10 miles to about any big box store from my house. So add $6 for the round trip.
Need to take a package to UPS? Five miles(x2). $2 for pickup seems like a much better deal than it was five seconds ago. $2 for an ATM? Not bad compared to the eight miles to the nearest branch. Go to best buy? Wait two days and get it from buy.com. Two day shipping = $6. In prior years, shopping online was about convenience. Now its about the mileage.