Not sure, why you are telling EUR to USD is not in favor for EUR? It might not always be as much and be shifting around, but today i save:
Example:
3000 PLEX package in store is 125 EUR
3000 PLEX at retailer is 125$ which would be 109 EUR at todays rate. And that value is even before possible discounts at the retailer.
I really do not know where your values come from. I think you have done the conversion direction in the wrong way or thought of it in the wrong way. 1$=0,87EUR as of right now. You want to pay the dollar amount and need to check how many EUR you need for that. Not the other way around. This requires that the seller lists the item in dollar, which is only true at the retailer and not at CCP of course. CCP want EUR from you.
EDIT: and you missed your options for the whole chain now, i feel sorry for you…it goes like this: buy discounted PLEX → buy them at retailer to do $/EUR conversion profit → get discount on top of that (3-10% depending on your history) → use the bought PLEX to buy discounted gametime in NES.
Thats the quadruple save chain. But in a recent blog about the new packages CCP also told that they want to prevent this metagame in the future if i recall correctly. So bad that you missed it. I don’t know if and when it will be possible again in the future. In the past it was frequently possible.