It's worth 10 caps, but in terms of how many old world USD? hard to say - any amount dropped at once appears as that one bundle, so assuming the bundle is only representative it should be 1 US dollar per "Pre War Money" item. Alternately, any one bill is worth 10 caps regardless of it's denomination, since there's only one type of pre war money, vs. several denominations of NCR dollar. So one pre war money is a single 1, 5, 10, 20 or whatever, and it's value is as an antique, not as money.
Pre-War Money has a value of 10. The amount you will receive depends on the person you are trading with, as well as your barter skill. More than whats in my wallet for sure
Given the state of the economy immediatley before the great war, it's likely that bills had a much higher number then the 1-100 amount we use today. No exact number is given, but it wouldn't be at all suprising for the american dollar then to be using the same scale as today's yen. (that is, 1k-100k bills)
Due to inflation (Their cars were several thousand dollars, often hundreds of thousands), dollar bills had a very low value Pre-War, but now they are just used as a common form of currency. Bills as a whole have a standard value between everyone, relative to how much you can talk them into giving you, averaging around ten caps (or one sierra madre chip).
Our cars cost several thousands of dollars now, but I know what you mean, the Fallout 1 Corvega was "only" $199,999, which only the most expensive cars cost now, and is about ten times the average of a real world car.
Its paper, its worth whatever you BELIEVE it to be worth. Economic systems are retarded.
- It's only an economic system if most everyone agrees it has that value, not just you. Even then it's like bottlecaps - people in the wasteland know that they're basically junk, but they need something that's not easily replicated to regulate their trade.