Objection! Unless 1 universal money is worth 4USD, maths shows that bottlecaps are actually worth two to three pennies! (Since someone's getting FO4 for 2240 caps)
And 100$ NCR is 40 caps... so approximately 1$ USD.
Probably what she paid in. :P
Outside their home universe, bottlecaps are literally worthless. This isn't just what they're made of or even inflation (which is still a valid complaint; your currency doesn't work if any modern society produces it by the buttload); it's the fact that the Fallout Universe produces literally nothing of value. The fact they don't have factories is WHY they use caps in the first place.
You see, bottlecaps are a fiat currency, which basically means "Not backed by gold; they're worth what the gov/people say they're worth" which works in-universe because they're limited and all that, but not so much anywhere else. They don't produce useful crops or particularly advanced tech; they can't even guarantee a lasting government in the wasteland. As far as I know, they don't have any noteworthy raw materials, either. You can't trade with them because they don't have anything to export. Their GDP is literally in the negatives and they're surviving off scraps leftover from previous civilization. Fallout-Verse is basically an economic suckhole where everything just loses value through wear and tear.