It is strange that MELE has a different price on Origin than on EA app. Both are official EA and should have the same price.
Is the region set correctly in both apps?
For your other question, it should not make any difference that it was already installed over Steam Epic.
Buying it again might be impossible. I tried locating it through Origin's store and it says it's already in my library, even though I first bought it through Epic. I'm trying to download it through Origin just to see if there's any difference this time. I think I first tried installing it through EA. We'll see what happens in 9 hours...
Thanks for letting me know.
It seems there is a fundamental difference in how games that were brought on different platforms are handled now.
