It's cheap for a reason. The books are riddled with errors, they offer no support at all aside from "here are books. test is on $DATE". There are forums but no instructors on them.
If you're already proficient at mathematics then it's good to get a diploma to state as much. But if you're looking to learn then it will be of little help.
I don’t do the Math degree but I’ve found the tutors for the Finance M.Sc. with SOAS reasonably responsive. It says they’ll respond within three business days and they do. I wouldn’t say the course readers are well edited or kept up to date but the textbooks are all good so far.
Having looked through the courses offered, I have to say that I am quite impressed. They are offering several interesting courses in Applied Math such as Game Theory, Optimization, and Statistical Inference. Overall it looks like a solid Applied Maths degree.
If you're already proficient at mathematics then it's good to get a diploma to state as much. But if you're looking to learn then it will be of little help.