Is becoming the chief editor of an academic journal a good job and does it pay well?

There is no pay! Being an editor for an academic journal is not a job in itself. If you are a well known expert and respected tenured university professor in that field, you might be asked to be on an editorial board, and maybe chief editor. You might get a small stipend or none at all. You still have your own research and teaching to do, although the university may lighten your teaching and administrative load in consideration of your work at the journal. 

it is very good for your vita and future prospects.  Pay?  not so good ... not much in academe pays well.

Being the editor of an academic journal does not usually pay, except for a small stipend in some cases.  It is considered "professional service."  It's quite an honor to receive that position, and it can help professors achieve promotions and/or tenure if they don't already have it at that point. It is a job that is done on top of your university teaching or research career, not instead of it.  Some schools will grant someone a course reduction or other similar adjustment to their schedule to accommodate this, but not all (not mine). 

I can't say from experience, though that would be one of the people at the top of the editorial staff, so more than likely it pays decent.