I realized that I haven't answered the question. These $400 also include the tests.
Fable ported "human fuzzing session" (the best bug hunter) from Go to Rust and used it to validate everything else.
I used hierarchical state machines, so a lot of my QA gates were encoded into the implementation — impossible states are, well, impossible.
(I ported first 80% practically in one shot, planning and then leaving Fable overnight to orchestrate). Then I added a bunch of features, so at the end I ported more like 150% of the original code, I added tree-sitter, and a bunch of syntaxes highlighters. At the end with all that, price went up to ~$650
(I ported first 80% practically in one shot, planning and then leaving Fable overnight to orchestrate). Then I added a bunch of features, so at the end I ported more like 150% of the original code, I added tree-sitter, and a bunch of syntaxes highlighters. At the end with all that, price went up to ~$650