Not in the same league (outlay) but I spent £300 16 years ago to get my class one PCV (bus driving licence).
I am now earning £25000 a year + bonus in a transport related job, I could not have got without my years of driving busses.
Not just lucky but I work in an industry that judges people on ability not on how much money they have to pay for type ratings.
If I had £20000 16 years ago I might flying for a living, but perhaps not earning much more.