not enough info to reproduce (language ? input ? why is the expected answer wrong ?)

fixed

You don't have any fixed test cases.

Why is it shaped like a butt plug?

Very nice. This is as close to an "objectively correct" solution as I can think. Proper use of relatively obscure built-in methods for which this problem is a textbook use case example.

Great job on finding some hardcore edge cases for the basic tests.
I WOULD be ashamed of having hardcoded the last few tests, IF my solution wasn't already passing all 100 random tests like 90% of the time. Maybe one day I'll get back to it and try to finish a proper solution.
Still, super stoked to have solved my first 1 kyu kata and ranked up to 2 kyu.

Worked like a charm. Thank you!

This is a CTF puzzle.

I'm guessing it's because it's strictly following the principle of single responsibility. Every function does exactly one thing. But idk, doesn't look great to me.

The right hand side of the || is only evaluated if the left hand side is zero (a falsy value). So the sorting prioritizes count (objects with higher count come first), and when both counts are equal, the next condition is used (alphabetical sorting, by src and then by char).

Was pleasantly surprised that this didn't require any fancy optimization tricks or mathematical simplifications.
This makes me agree with the comment below that this is 6kyu max, but then I remember that most people are freaked out by the big math symbols xD

if the tax is 12% for example (t = 0.12), then what remains is 88% of your earnings. 1-t = 0.88. This is the number by which you should multiply your earnings.

It definitely does not require regex.

1kg makes up 1% of 100kg, but the same 1kg makes up 2% of 50kg.