The expensive part is reaching the address
A postal route costs money whether a carrier delivers one letter or several. The vehicle, labor, and time required to travel a long stretch of road are spread across the items on that route. In a city, many deliveries can share a short walk or drive; in a remote area, the same travel may serve only a handful of homes. That makes the cost per delivery much higher.
The comparison is not simply the price of a stamp against the fuel used for one letter. Delivery costs include the whole network needed to collect, sort, transport, and hand off mail, along with the final trip to the address. A remote letter may bring in less revenue than the portion of those costs it effectively uses.
Why the route still runs
A service that promises delivery to every address cannot choose routes only by profitability. If it skipped sparsely populated places, residents and businesses there would lose access to the same basic mail network available elsewhere. Keeping those routes also supports practical needs such as receiving documents, orders, and other correspondence.
That promise creates a tradeoff: some deliveries cost more to provide than they earn directly. Revenue from denser, cheaper-to-serve areas can help support the wider network, while postage is generally set for broad classes of mail rather than recalculated for each recipient’s distance from a sorting center.
The result is that a stamp buys more than the movement of a single envelope. It helps pay for a system built to reach the last house on a long road, even when that house is the only stop for miles.
