In many places it isn't essential. But if you want a higher paycheck than I would advice to get one as companies want to recruit people who are more experienced in the field. Personally I would highly recommend getting one.
In my field, experience matters more than a master degree. The problem with masters degree (if you are doing it full time) is that it will cost you at least two years of your experience. In short, you need to put in a lot of time and effort and in the end you will have to contend with a reduced salary.