OK. I want to do a MSc in economics because I want to know about economics.
There is no 'grand plan' nor is there any desire to go into a job which requires economics. This is a purely academic decision.
This is the field I want to study next. Sure, having the degree looks good on a CV, but that is largely besides the point. Out of all my areas of interest, I think this is the best one to do. I could study philosophy or something, but that seems to be something I can do on my own initiative.
As to the maths question, I too would like to broaden my skills in this area. I was kind of hoping an economics course would be like reading a book by J. K. Galbraith, but I feel that is not the case.
Also, I have an insatiable desire to be mark and graded* which private study doesn't provide.
*not degraded, ok MM?