Sleepwear: yes, weird archaic thing.

US "First class" is typically a misnomer.

I spent so much much time, money and effort abusing mileage programs between like 2009-2016. I think the the whole thing started with the oil glut following the 2008 crisis.

E.g. US Airways Dividend Miles (USDM) was a goldmine. They kept having these sales where you could buy "miles" for extremely advantageous rates. You could then redeem those "miles" in their partner airlines' flights. They were buttering themselves up to be bought by AA. This went on for years.

End result: You'd pay maybe 1400USD for a return first class ticket on e.g. Qatar Airlines between Copenhagen-Doha-Tokyo, or something similar. If you'd buy a ticket it would be 3-5x more.