IELTS
The world most expensive English test.

Speaking and writing tests are highly depends on the marker's preference, so basically the results depend on your luck.

Getting 7 or 8 bands on each subject (Listening, Reading, Speaking, Writing) is the same situation that you roll 4 dices and get more than 5 or 6 on each dice.

Some very unlucky people spent more than $10,000 on that.
I got IELTS speaking score 8 last week, but 6 this time. The interviewer might dislike my hair.