(Master's Degree) What are they 'precisely' looking for in a Statement of Purpose, and does a SOP matter when one has excellent GPA?

(N.b. All my questions are concerning applying for a Master's degree)

I have read a lot of websites, articles, extracts from different books about the Statement of Purpose (Motivation Letter). I'm still not quite sure how to write a 'breathtaking' SOP to blow the reader's brain.

For example, I don't know how to present my interest in my field of study in a brilliant way to amaze the person reading it. I am very interested in my field and I can think of million things I can do with it, but still I don't know the best way to present that interest. Most people say that I need a 'grip', an interesting story from my own life that made me become interested in my field of study. But let me be honest, I have none, not everybody has that sudden 'turning point' in their life. My interest in my field of study just happened over time; one day I saw that, hey this is pretty a fascinating filed of study and it totally matches my interest in different fields, I can apply the knowledge gained from this field to almost anything. So nothing extraordinary, it just happened with no reason.

I have also read hundreds of samples online, and they all look totally the same, they say that SOP has to be distinctive, but that's exactly what I didn't see in the samples I read - they all start with a memory of their childhood and finish with how much they'd love to contribute to society and mankind and become a researcher.

I am really lost about writing a SOP. I think I'm even more lost because I have read thousands of articles and books and have heard a lot of different opinions for the past 2 months. I am not sure what a "superb" SOP is, and I am not quite sure what the admission committee looks for...

Finally, I have a tiny last question; Does the Statement of Purpose matter as much if one has a GPA of 92%?