First, I am not native English speaker so I do not understand all nuances of this language. Why flipping burgers seems to be the worst insult here. "You are lousy photographer you should be flipping burgers instead". My mom always said to me that it's not shame to do any work.
Unlike what's been said above, my take on 'flipping burgers for a living' is that it's a hot, sticky, sweaty, stressful job with zero respect, which leaves your hair and clothes (under the naff uniform) stinky every day, yet pays peanuts.
Yes, Sue's right. It is usually used to compare with something same that is not so fantastic too.
Like Racephoto , sub 25 cents per download? I prefer to flip burgers. But now in many places you don't flip burgers,
you busk in the street sing songs with your guitar and make more money than people in the office .