Has the cost of building software dropped 90%?

I am on the free tier of Gemini 3. With some intervention on my part, I got it to build, in Emacs Lisp, a primitive-recursive function for determining if a number is prime (by mu-recursive I mean a function built from the building blocks of a constant, successor and projection function, as well as a primitive recursive function and compositional function/macro). I was impressed, as previous models (including Anthropic and OpenAI) could not do this.

For the past few days I asked it to built a mu-recursive Ackermann function in Emacs Lisp (built on the primitive-recursive functions/operators, plus an extra operator - minimization). I said that the prime detector function it already built should be able to use the same functions/operators, and to rewrite code if necessary.

So far it has been unable to do this. If I thought it could but was stumbling over Emacs Lisp I might ask it to try in Scheme or Common Lisp or some other language. It's possible I'll get it to work in the time I have allotted from my daily free tier, but I have had no success so far. I am also starting with inputs to the Ackermann function of 0,0 - 0,1 - 1,0 - 1,1 to not overburden the system but it can't even handle 0, 0. Also it tries to redefine the Emacs Lisp keyword "and", which Emacs hiccups on.

A year ago LLMs were stumbling over Leetcode and Project Euler functions I was asking it to make. They seem to have gotten a little better, and I'm impressed Gemini 3 can handle, with help, primitive recursive functions in Emacs Lisp. Doesn't seem to be able to handle mu-recursive functions with minimization yet though. The trivial, toy implementations of these things. Also as I said, it tried to redefine "and" as well, which Emacs Lisp fell over on.

So it's a helpful helper and tool, but definitely not ready to hand things over to. As the saying goes, the first 90% of the code takes 90% of the time, and the last 10% of the code takes the other 90% of the time. Or the other saying - it's harder to find bugs than write code, so if you're coding at peak mental capacity, finding bugs becomes impossible. It does have its uses though, and has been getting better.