IMHO the best reason to get a master's is because you want one. For you. Not to fill a spot in a resume or check off a box on some application. You can go learn all of it yourself with self-study if that's what you're after (much of the curriculum and lectures are freely available), and I really think the value to a potential employer is fairly limited aside from some narrow corner cases. And if you fall into one of those cases you probably know it already.

So get it if you think the feeling of satisfaction and achievement is worth it. The major cost by far is not money, but time, be aware.