Ah, yes... whether it is more lucrative to get the Master's degree or follow the immediate employment track. My advise is always to follow your heart -- or as Joseph Campbell used to say, "Follow your bliss!"
But, it probably comes down to your priorities. Do you want to be happy, or do you want security. Both are possible, but you have to be willing to settle for less money/security/"certainty" in order to do what you really enjoy doing. And it works best if you are doing what is in harmony with your "mode of service" -- i.e. your particular, unique contribution to life on this planet (like the boy scout credo to always leave a campsite cleaner than it was on arrival). Your particular, unique contribution is what comes of applying your unique set of abilities and preferences to the higher purpose of service. This is the track to ultimate satisfaction.
But, not everyone sees that, so go with what your level of vision guides you to do. And then do it well, whatever it is.
BTW, I put "certainty" in quotes, because _certainty_ is an illusion -- as is _security_. Neither really ever exist--even when they seen immutable (I live in Earthquake territory , so I know what I'm talking about

).