Has the cost of building software dropped 90%?

As I said in a previous post:

I think the 90/90 rule comes into play. We all know Tom Cargill quote (even if we’ve never seen it attributed):

The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time.

It feels like a gigantic win when it carves through that first 90%… like, “wow, I’m almost done and I just started!” And it ‘is’ a genuine win! But for me it’s dramatically less useful after that. The things that trip up experienced developers really trip up LLMs and sometimes trying to break the task down into teeny weeny pieces and cajole it into doing the thing is worse than not having it.

So great with the backhoe tasks but mediocre-to-counterproductive with the shovel tasks. I have a feeling a lot of the impressiveness depends on which kind of tasks take up most of your dev time.

If your job is pumping out low-effort websites that are essentially marketing tools for small businesses, it must feel like magic. I think the more magical it feels for your use case, the less likely your use case will be earning you a living 2 years from now.

Yeah, I think the more your job demands correctness in novel scenarios the less impressed you are with these shiny demos. I encourage anyone to pause the demo once the thing is generated and stare at what it did. Is it genuinely correct and impressive? Are you impressed because it made a thing generally shaped like what you expected, or because it would be genuinely impressive (or even adequate) if a person did it?

you are right, but the inverse doesn't have to be. There is a factor that could make the work so cheap, that people don't care about the quality anymore.

Fully agreed, aligns perfectly with my experience hitting the 95% done wall on a solo contract project recently. I still do the majority of work using agentic tools but the multiplier effect feeling evaporated at a certain point as the accumulated tech debt, complexity and scope creep enabled by how “easy” features felt with Claude Code/Codex early on finally caught up to me.

I (probably) still would have used CC heavily with benefit of hindsight but with a view that every seemingly “trivial” feature CC adds in the greenfield stage to be radioactive tech debt as the pile grows over time. Until reaching the point where CC starts being unable to comprehend its own work and I have to plan out tedious large scale refactors to get the codebase into a state approaching long term maintainability.

One thing I've noticed is that Claude is so good at doing things that I've asked for, that later on I realise that I shouldn't have even been doing them because they're stupid or unnecessary but Claude was just cheerleading me on and emoji spamming tick marks so that I didn't realise there was very little purpose to the feature.

Yeah once you start working at the feature level, you’re into product design, and that’s an entirely different realm of working that, IMO, shouldn’t even involve code. Even higher-level software design —e.g. broad stroke architecture like figuring out your data model and how it will be accessed— is better off being done before any significant amount of code gets written. Claude, et al will happily walk you straight off a cliff if you ask it to, and not having that stuff sketched out ahead of time is a most efficient way of accidentally doing that.

It’s always tempting to start writing code before you really know what you’re going to build because it’s so satisfying and exciting to see an idea take shape. I know I’ve had more than one or two projects where I started writing before I understood the shape of the problem I was solving and ended up a few hours into the project with a useless pile of stupid. It seems like LLMs can lead you much further down that road because it just seems so magically productive.

The only way that state would be sustainable is if we suddenly solved code vulnerabilities, or the damage they cause.

Most companies have more than enough of those, and these problems are already solved every day. In the end everything is vulnerable and the internet is dangerous, a vibe coder is no more dangerous than an average junior software engineer.