Exclamatory Did you ever? is just a slightly more "non-intuitive" idiomatic construction than Well I never!. The choice of first, second, or third person singular as the subject makes no real difference to the meaning in...
1: Well I never!
2: Did you ever?
3: One would hardly think so!
...where the only real difference is that although it's perfectly natural to use I or You in #3 above, it's not idiomatic to change the subject like that with the first two. But other than that, they all mean pretty much the same thing (speaker is expressing HIS OWN surprise and/or rejection of something contextually relevant).
It's not really worth trying to deconstruct the grammar or "origin" of expressions like this. Most native speakers are perfectly familiar with the expressions themselves, but wouldn't have a clue how they came to become part of natural spoken language. This doesn't stop us using them, but note that #1 and #2 in particular are starting to become rather "dated, stylised" today.