Walmart vs. United Supermarkets: a statistical breakdown

I, like most of you, sometimes wake up in the middle of the night and ponder the Walmart dilemma. If I factor in my time, is it actually cheaper to shop there? So, I decided to conduct my own little experiment. I bought the same items at each store and timed my trips. I started the timer when I entered each parking lot and stopped it as I exited each parking lot. If you think this is nerdy you should see my spreadsheets comparing the finances of various republican parties (here you go: http://www.tommechler.com/media/party-finances-2007-2009-b.pdf). Anyhoo, here are the results:

Walmart
$3.88 1 Gallon milk
$1.99 1/2 lb Smoked White Turkey
$2.38 Peanut Butter
$1.32 Grape Jelly
$1.00 White Bread
$3.38 16 American Singles Cheese
$3.56 2.45 lb Red Seedless Grapes
$1.91 1.5 lbs Gala Apples
$1.20 2.45 lbs Bananas
$1.76 2 Bags Blueberry Muffin Mix
$1.18 1 Dozen Large Eggs
Total: $23.56
Total Time: 17 minutes, 45 seconds

United
$3.99 1 Gallon milk
$2.00 1/2 lb Smoked White Turkey
$2.97 Peanut Butter
$1.49 Grape Jelly
$1.29 White Bread
$2.39 16 American Singles Cheese
$3.18 2.45 lb Red Seedless Grapes
$2.00 1.5 lbs Gala Apples
$1.44 2.45 lbs Bananas
$1.98 2 Bags Blueberry Muffin Mix
$1.29 1 Dozen Large Eggs
Total: $24.02
Total Time: 17 minutes, 13 seconds

So, the numbers are suprisingly close. I expected Walmart to cost a ton less, but take a lot longer. I know what you are thinking: "But Josh, if my time is worth money, how much did the extra 30 seconds at Walmart cost?" Glad you asked. The average annual income in America is $52,029. That works out to about 43 cents per minute assuming a 40 hour work week with 2 weeks vacation per year. The extra 30 seconds cost 21.5 cents. 1 minute longer and Walmart would have been more expensive. For the average Amarilloan (who has this exact grocery list, who makes exactly $52,029 per year, who is cheap and buys generic brands, who wastes no time fraternizing with people at the store, who shops at exactly 9:15pm on a Sunday evening) it is cheaper to shop at United if Walmart is more than a 1 minute further drive. Praise God I'm closer to United.

One other fyi, I have heard rumors that United marks down name brand items at the first of the month and generic items at the end of the month.