I know that Magento uses Base Currency and Display Currency for different purposes. Display Currency is just for the front-end and it can use Magento Conversion Rates to convert the prices automatically. Base Currency is used to process payments and this is the information sent to PayPal or other payment gateways. More info here.
For example: You can have 2 websites, both using US Dollar as Base Currency. And one of them you change the Display Currency to Canadian Dollar and set a conversion rate for that. The Canadian website will convert product prices to show it in Canadian Dollar, but once the user go to checkout, the currency used will be the Base Currency (US Dollar).
The only solution I found is to have a Base Currency for each website, but then you need to set the product price for each website as well.
In our case, we have more than 1,000 products and 4 different currencies. So, I would need to set the US Dollar price, Canadian Dollar price and any other currency for each product and this is a huge work.
Is there a way to make this work of setting different currency prices for products easier? Or is there another solution to my problem? (Send the display currency to the payment gateway).