If your situation will allow you to, do the masters. A job at Amazon will always be there for you, but once you get a taste of industry it's hard to go back into academia. Looking back, I wish I'd done more schooling and taken more advantages of the opportunity available to me back then.

Flexibility and money are your long term goals, and the masters opens more doors to that than getting into industry today. What subfield would you be getting your masters in?