The easiest thing to do is to quote the price in your local currency. Go the extra step and convert it to a currency they understand.
If you are not sure what currency to use, just use US Dollars, which is the international currency.
Of course, if you are dealing with somebody regularly, then you should know their preferred currency.
Use local currency. E.g. Australian company billing someone in Australia:
Our price is $1,000
❌ Figure: Bad example - The client doesn't know whether it's AUD or USD
Our price is AUD $1,000
✅ Figure: Good example - AUD makes it more clear
Use their local currency. E.g. Chinese company billing someone in Australia:
Our price is CNY ¥1,000
❌ Figure: Bad example - The client will need to convert it
Our price is CNY ¥1,000 (about AUD $160)
✅ Figure: Good example - AUD gives a clear understanding of the costs
Use USD. E.g. Chinese company billing someone in Brazil.
Our price is CNY ¥1,000
❌ Figure: Bad example - The client will need to convert it
Our price is CNY ¥1,000 (about USD $160)
✅ Figure: Good example - USD gives a clear understanding of the costs