They are essential, but they can be purchased cheaply. There are fruits that are expensive. Organic foods are especially expensive, but they are not necessary to a healthy diet.
I disagree with B_L about obesity. Fat people are fat because they don't take care of themselves. Some have to work harder than others, but that is life. I wasn't gifted with a 95 mph arm. Some people are. I had to work harder than most to compete at a high level. Some people have to work harder than others to maintain a healthy BMI, but everyone can do it.
Also, remember that skinny doesn't mean healthy.