Just like burger's aren't all created equal, neither are pictures of burgers!
Why is food photography so important? Why would you want to hire someone to do it vs. buying a point-and-shoot and saving some $?
You can't hear, touch, taste, or smell a photo of a burger.
The photo has to do all the work when you only have one sense at your disposal, and seeing is believing. If that burger doesn't look juicy, hot, sizzling, and downright mouthwatering, then who's going to believe that it is?
Let your photos reflect the deliciousness of your food. Hire a professional!