I have to say that I think your equation is insufficient.

For one thing, it pays $6.15/hour for the trip to the liquor store in Superior, but not to the one in Duluth. It should pay for the difference between trip times, unless of course that it assumes a 0-minute trip on the Duluth side, for example if you live upstairs or next door to a liquor store.

Second, it fails to take into account wear-and-tear on your vehicle. The IRS's mileage reimbursement rate (for wear-and-tear plus gas) is currently 55 cents/mile. This boosts compensation for your 8-mile trip from $.90 to $4.40 -- a substantial increase.

I posit that the Superior trip for financial reasons is invariably a falsely perceived savings. It's only after 10pm and on Sundays that the opportunity cost outweighs the extra financial loss.

Wrong? How so? If that isn't the law, please tell me what is.

Rob: Ah, I see now. I thought you were going to say that $45 for a case of beer wasn't overpriced. To which I would say: Well, then what do you care about saving two bucks?

My comments were not meant to disparage the hard work Paul has done, either. I just think it's funny to complicate matters. This matter still isn't complicated enough for my tastes. There needs to actually be an equation, with variables for distance, gas price, gas mileage, and so forth.

Using new your equation, if I bought $9.99 in alcohol at the Shanty on East 4th Street, the actual cost would be $11.54. Purchasing the same $9.99 item just across the bridge at the Hammond would amount to an actual price of $15.99. That's $6 MORE to purchase my beer in Soup Town. Now, the retail price of the exact same item might be cheaper at the Hammond, but it sure isn't going to be $3.99 or less. 

I calculated that I'd have to spend $89.75 (in a single trip, mind you) before I would even break even buying liquor in Superior instead of Duluth. 

(My distances and times were estimated using Google Maps' Driving Directions feature. I paid myself minimum wage to make the purchase.)