As for currency, I usually sub in won and then put approximation of USD amount in parenthesis. For example, I'd put something like "500,000 Won ($500)"
Since I live in America, I mostly translate for those who are familiar with USD. I don't assume most people would know how much 500,000 Won would be, just like I forgot how much 500,000 Lira is in USD. Although I don't calculate exact conversion using that day's conversion rate, if I put in approximation in dollar, it will give viewers general idea of how much they are talking about.
I know that $ symbol is used for other countries, too. But it looks really strange to put in "500 USD" to me. So I just do what I can to cover what I know.
I'm assuming other language subbers will translate that amount into their own currency, either using the actual amount in Won or using the approximation of US dollar amount.