It’s not code. It’s a matrix of associative conditions. And, specifically, it’s not a fixed set of associations but a sort of n-dimensional surface of probabilities. Your prompt is a starting vector that intersects that n-dimensional surface with a complex path which can then be altered by the data it intersects. It’s like trying to predict or undo the rainbow of colors created by an oil film on water, but in thousands or millions of directions more in complexity.
The complexity isn’t in understanding it, it’s in the inherent randomness of association. Because the “code” can interact and change based on this quasi-randomness (essentially random for a large enough learned library) there is no 1:1 output to input. It’s been trained somewhat how humans learn. You can take two humans with the same base level of knowledge and get two slightly different answers to identical questions. In fact, for most humans, you’ll never get exactly the same answer to anything from a single human more than simplest of questions. Now realize that this fake human has been trained not just on Rembrandt and Banksy, Jane Austin and Isaac Asimov, but PoopyButtLice on 4chan and the Daily Record and you can see how it’s not possible to wrangle some sort of input:output logic as if it were “code”.
$1M a shot seems like a lot until you look at what goes into each one, how much development costs, and the environment it is designed for. You don’t need corruption to make these expensive. Also, the are based on 30 year old technology. Rather than being cheaper than new, they tend to be more expensive due to requiring miniature mechanisms which were cutting edge in 199x. And there are no other uses for them in their hardened configuration so you don’t get economy of scale of something like a commercial ship or board. Plus there’s a lot of paperwork and you can’t sell a single piece unless the government approves it. This is so far from a consumer item there isn’t even a way to compare costs.
FWIW, corruption would cost roughly the same price but you’d receive a missile with shoddy components and forged paperwork. Just look at Russia’s army to see the difference in munition reliability.