Cheap to Build, Expensive to Keep

The new economics of software in an age of effortless creation.

In the early 1970s, a mathematician named Meir Lehman sat inside IBM and did something almost no one thought to do with software. He watched it age. Most of his colleagues treated a program the way a mason treats a wall, as a finished thing, mortar set, purpose fixed. Lehman had access to the release histories of IBM’s OS/360, one of the largest and most ambitious operating systems ever attempted, and when he laid the successive versions one after another he saw not a wall but a river. The thing would not hold still. Each release grew more tangled than the last. Fixes bred fixes. Structure that had once been clean silted up with exceptions, patches, workarounds, the accumulated debris of contact with a changing world. Left alone, the software did not simply endure. It rotted.

From this Lehman drew a set of laws, and two of them still hum with a strange authority. A program that is used must be continually changed, or it grows progressively less useful. And as it changes, its complexity increases, unless deliberate work is done to hold that complexity down. He had, without quite saying so, imported an old and terrible idea out of physics and into the world of code.

An Old and Terrible Idea

Rudolf Clausius had given it its name in 1865: entropy. He invented a word to describe the one direction in which the universe seemed unwilling to run, which was backward. Heat flows from hot to cold and never the reverse. Order, left to itself, decays into disorder. Every transfer of energy pays a tax, and the tax is never refunded. Clausius was thinking about steam engines, about the melancholy fact that no engine can ever be perfect. But the second law does not care about engines. It is a statement about time itself, about the way any organized thing, a crystal, a cell, a company, an operating system, tends to slide toward sludge the moment you stop pushing against the slide.

A Program Is Not an Object

No one tells you this when you learn to build. A program is a process held briefly against entropy by human attention, and the moment the attention wanders, the decay resumes. The dependency you never chose ships a change and your careful structure cracks. The interface you built against quietly moves. The model underneath your clever workflow shifts by a fraction of a degree, and the assistant that summarized your inbox flawlessly in June begins, in July, to invent meetings that never happened. Nothing broke, exactly. The world simply moved, as worlds do, and your creation did not move with it.

This decay was hidden, for most of my career, behind a larger cost, and the larger cost was the building. Writing the code was slow, expensive, the long middle of every project, and because it dominated the front of the ledger it dominated the imagination. We came to believe that construction was the hard thing. We built our entire mythology of the engineer around the act of creation, the lone author at the keyboard translating thought into instruction, line after line, and we let the quieter labor that came afterward, the tending, the patching, the endless small resistances against entropy, fall into shadow. Maintenance was janitorial. Building was art.

The accountants knew better, and had known for years. Barry Boehm spent the 1970s measuring where the money in a large system actually went, and he kept arriving at the same uncomfortable figure: more than half of a program’s lifetime cost, in many systems closer to seventy percent, was spent after it shipped. The keeping already cost more than the making. We never felt it, because the building arrived as a single dramatic bill and the keeping came diffuse, spread thin across years, a line item no one dreads the way they dread a construction budget. The larger cost was hiding in plain sight, at the bottom of a ledger we refused to read all the way down.

The Toll Booth Removed

Then the agents arrived, and they went straight for the part we had mistaken for the whole. Describe a tool in a paragraph and it exists before lunch. The long middle of Lehman’s river, the expensive stretch of pure construction, has narrowed almost to nothing. The tide has gone out, and the rocks lie bare. Creation was never where the entropy lived. Entropy lives in persistence, in the days and months after the thing works, and no agent has repealed the second law. It has only removed the toll booth that used to stand in front of it, the two weeks of effort that once made you ask, before you built a thing, whether it truly deserved to exist. Take that friction away and you take away the question. What remains is a person, a machine that never refuses, and a growing shelf of small programs, each one a process quietly demanding to be fed, each one sliding, the instant it is forgotten, back toward sludge.

The Coal Question

In 1865, while Clausius was naming the tax the universe levies on order, an English economist named William Stanley Jevons was worrying about coal. The engineers of his century had made the steam engine far more efficient, wringing more work from every lump, and everyone assumed the obvious would follow: a more efficient engine would burn less coal. Jevons watched the opposite happen. Cheaper power multiplied the uses power could be put to, until Britain was burning more coal than it ever had, precisely because each ton now did more.

Make a thing cheap enough and you do not get less of it. You get a flood, and every drop in the flood carries its own long tail of consequence. The cost of producing software has fallen the way the cost of mechanical work fell in Jevons’s England, and we are answering it exactly as the Victorians did, by building everything: a personal tool for every passing annoyance, a script for every whim, a small app to solve a problem we will have forgotten we ever had. Each of those creations is cheap to build and expensive to keep. We have manufactured a fleet of small engines, every one of them running down, every one of them demanding to be fed. The bill for making fell to almost nothing. The bill for keeping went up, because now there is so much more that has to be kept.

The vibe coders are learning this now, one abandoned project at a time, and they are learning it in the oldest possible way, which is by paying for it. What they are rediscovering is not a fact about software. It is a fact about the universe, one Clausius saw in his steam engines and Lehman saw in his release notes and every one of us eventually meets a long list full of things we built because we could. The making was never the cost. The keeping is the cost. It always was.