I think that most of our tropes about magic, the 'cost' etc are very binary and Monotheist/Paradigm oriented.

Paradigms are culture stuck in a mindset perhaps. Unable to see other realities. My best example is that fairly Christian oriented people can't conceive of people like me being Neo Pagan or whatever you want to call it, but finding reverence if not worship for deities from pre-Christian eras.

So I think a lot of our and Western culture's look at these stories is that they should serve as morality plays.
It may seem a stretch for comic book stories, but the influence of a paradigm on culture is pretty far reaching.
Many people can only conceive that there is 'God' and therefore there is 'Satan', and most of our great literature from ages ago, reflects that. Mephistopheles anyone? So this is why some expect or feel bargains or costs are involved with magic, but when you learn other cultures and times stories of magic, Gods, Goddesses and the like, the concept is more fluid and usually more organic.