In 1E there was always a bit of a discrepancy with the economy, as in, how much a GP was worth, specially when calculating the value of some goods vs how much people made.
I always explained to my group that a rough estimate would be 1gp = 100 USD in a 1970s economy. It wasn't perfect but it gave a rough idea.
I haven't had the chance to delve into the book in too much detail yet, but was wondering how this is looking so far now that they've revamped stuff a bit.