How can I have a sales price and a cost of sales in a different currency?

Thanks for dropping by, dubai-caulaincou.

I can share some information on how multi-currency works in QuickBooks Online.

In QuickBooks, there isn't any option to display foreign currencies in your product and services since your inventory items are linked to Income and Expenses which are defaulted to your home currency. 

On the other hand, you have the option to turn on multi-currency and set up your suppliers or customers in Euros or other currency of your choice. That way, if you'll create a bill towards a Euro supplier or customer with your home currency being in Emirate Dirhams, QuickBooks displays the totals both in Euros and Dirham. Take note that once the feature is turned on, there isn't any option to turn it off.

Here's how:

1. Go to the Gear or Settings icon.
2. Select Account and settings.
3. Click Advanced.
4. In the Currency section, hit the Edit pencil icon.
5. Choose your Home Currency.
6. Checkmark the Multicurrency box and confirm that you understand that you can no longer undo it once the option is turned on.
7. Click Save and close.

For more information, check out this article: Turn on and use multicurrency.

Also, I've got this helpful resource for more insights:

• Assign a foreign currency to a customer in QuickBooks Online.

• Add a supplier with a foreign currency in QuickBooks Online.

Let me know if you have further questions about managing your currency. I'm always here to help you.