One Trip, Two Stores And The Cost Of The Detour

Splitting a shopping trip across two stores to get better prices on each is a common strategy. It has a cost that is easy to leave out because it is not paid at a register.

Driving has a per-mile cost beyond fuel

Tires, brakes, fluids, depreciation and the eventual repairs all accrue with distance rather than with time. Fuel is the visible part of a larger figure.

Because the other components are paid later and in lumps, they feel unconnected to any individual trip.

Using a per-mile estimate rather than a fuel-only one changes which detours make sense, sometimes substantially.

Time is the larger line for most households

A detour that adds twenty minutes of driving plus the walk, the aisles and a second checkout can consume close to an hour.

Whether that matters depends on what the hour would otherwise be used for, which is why the same detour is sensible for one household and not another.

Counting it at zero is what makes marginal detours look free, and that assumption is the usual source of the error.

The saving has to be measured on the basket

A second store is usually cheaper on some items and more expensive on others. The relevant figure is the difference across everything actually being bought.

A large percentage saving on a small purchase is a small amount of money, and it is the amount, not the percentage, that has to cover the driving.

Written out this way, many two-store routines turn out to be preserving a habit rather than capturing a saving.

Routes and frequency change the arithmetic

A store passed on the way home carries almost no detour cost, so the same price difference is worth capturing there and not elsewhere.

Consolidating specialty purchases into an occasional larger trip spreads the driving across more items, which lowers the cost attributable to each.

Both approaches attack the fixed cost of the trip rather than the prices, which is where the recoverable money usually is.

Extra stops cost more than mileage

Each additional store adds exposure to unplanned purchases, and stores are arranged to encourage them. The additional basket often exceeds the saving that motivated the stop.

Delivery and pickup services change this again by removing the aisle entirely, at a fee that can be compared directly with the driving cost.

The comparison is not between shopping and convenience but between two ways of paying for the same errand.