Heroes of Might and Magic® 4: Complete on my wishlist is priced 1,29 euros (with discount -85%) but when I try to add it to cart it changes price to 2,19 euros (with discount -74%), which is the correct price then?

Both. The Heroes of Might and Magic games are in a bundle in the front page. Buy (or complete) the whole bundle to get the 85% discount, or buy individual games with a 75% discount.

Ok, thank you, got it! Still it was a bit confusing :/