@ksusha64 if you see this post by Dan.com you can see that they received 49,506 EUR and they sent you back 49,506 EUR. So in no way they have gained anything, because they did not convert any currency.
So, here we go. Who converted from usd to euro, and then from euro to usd? There you have it, your bank.
Now let's see what happened.
On Dec 6, you sent 49,506 EUR and you say that you paid "around $58,000 USD" for it.
I paid around $58,000 USD for it.
Since I paid 49,500 in euros
Well, there you have the first $2,000 of conversion fees that your bank charged you. You should have paid $55,852 usd for sending 49,506 EUR as of Dec 6 usd-eur exchange rates, but your bank charged you a 3,8% of conversion fees if you paid $58,000 usd).
https://www.xe.com/currencytables/?from=USD&date=2021-12-06#table-section
Then, the second $2,000 of loss, when Dan.com sent you 49,506 EUR on Dec 10. You should have received $56,008 usd as of Dec 10 usd-eur exchange rates, but your bank charged you a 3,7% of conversion fees, and you only received $54,000 instead of 56,008 usd).
https://www.xe.com/currencytables/?from=USD&date=2021-12-10#table-section
I just have seen the amounts sent, usd charged, eur received and exchange rates, so I thought to let you know so you can see who took the $4,000 of your loss.
I am not a bank expert, just trying to help you understanding what happened with your lost $4,000.
@ksusha64 ask your bank for the conversion fees they charge to convert from usd to eur and from eur to usd. Maybe you find there the answer.
I know some banks charge a high amount (around 3%) to convert between currencies. They are who make business with these conversion fees.