A call girl is a female prostitute who arranges her “services” via telephone, though I tend to believe that Capote intended for her to be more a female escort, hence the term “American geisha” he dubbed her. According to Capote: “Holly Golightly was not precisely a callgirl. She had no job, but accompanied expense-account men to the best restaurants and night clubs, with the understanding that her escort was obligated to give her some sort of gift, perhaps jewelry or a check … if she felt like it, she might take her escort home for the night.”

Back then there was a restroom (powder room) attendant whom you tipped. The men she was with would give her $50 to tip the powder room attendant, but of course she’d most likely keep it for herself.

The setting is c. 1943/44, so $50 then would be about $623-$612 now according to this calculator.