On my quest to get more euros, I've found out that the traders charge more than they should for dollars and euros. This isn't entirely obvious to someone who just uses the euros/dollars for quests. According to the
Thankfully, EFT has an implemented feature to show you how much X costs in roubles if you put it up for Y amount in euros/dollars. When you put an item up for sale, you can put it up for sale in a different currency. When you do this, you get an "est." on the bottom right of the item to show you the estimation in roubles it costs, when compared to your price you put up in euros/dollars. As you can see in the screenshot
For instance, you need 50k euros for the quest, "Mentor". Buying all 50k euros at Skier's rate of 145 roubles per 1 euro, you would spend 7,250,000 roubles. If you were to get your euros by selling on the market, you're gaining that 50k euros slowly at a cost TO YOU of 126 roubles per euro (that is 126 roubles in "lost" profit because you are selling in euros and not roubles.) That adds up to about 6,300,000 roubles "spent" in order to get your euros for the quest. This is nearly a million rouble difference!
It may not seem like much, but I think it's important for people to understand because it can save you money, even if it's a little bit by your standards. I've recently began selling in euros instead of roubles since I have a decent cushion in my stash, and to my surprise, people buy suprisingly fast when it's in euros. Maybe a majority of the playerbase don't care about their euros? Or they simply click the first offer and don't realize it's in euros, lol. I'm already at 11k euros from quests, loot, and beginning to sell in euros as of yesterday. It's adding up quick, and I'd highly reccomend you do the same if you are looking to increase your foreign currency.
P.S. The rate apparently changes often, according to the wiki, so you should always check that the rate is the same whenever you do your calculations to put up a fair price on the market. 1 euro is equal to 126 roubles today, but it can very well change the next day. Check using the est feature every now and then to make sure you're not losing out on more profit.
Source: https://www.reddit.com/r/EscapefromTarkov/comments/sgk9kq/sellings_items_for_eurosdollars_buying/