Another thread reminded me of this, so I did a search:
BABY TRAILER INSTEP
Let's see, gas is $3.45, and let's say that I get 40 MPG city, although the grocery store is two miles away.
$50 / $3.45 = 14.49 gallons * 40 MPG = 579.7 miles.
So, not counting the 26.2 miles each way to the person selling the trailer, I will break even once I get groceries 145 times!
If I use it once weekly, that would only require two years, nine months, 13.5 days!
However, that also saves wear-and-tear on my car, and since I do my own maintenance, that takes forever!