Social justice?

You know, actually I'm not sure what the term "social justice" is... If anyone has a better definition, please comment. To me, I understand it as a statement to indicate the differences in "justice" in regards to social standing. For example, A rich person who can afford to hire a high power lawyer can often times be found not guilty as opposed to a poor person who must settle for a public appointed attorney. Or a smaller example would be how if you are dressed in an expensive suit, you are treated differently by someone in say dirty jeans and T-shirt.
I also view the term "social justice" as something that relates to class (eg: poor vs rich). So the other day, I was hearing how a barrel of oil is now at it's all time high (last I heard $107 a barrel). Then I've seen how Gas prices have really jumped to reflect this as well. We're up around $3.07 a gallon now for Regular. Then I thought... you know, I've never heard a comparison of a rich person's income to a poor person's income. It struck me as odd, that I'd never heard it before. I wonder why? So I actually did some math to make my point.
Wealth is relative. You never have enough and you always want more. But I was trying to figure out how can rich people relate to poor people (and vice versa) there should be a common factor here.
So here's something to think about. (I don't really have a point here, I'm just putting this idea out there in the hopes that someone thinks about it besides me).
Please don't take offense at my example, I'm picking the numbers mainly because I didn't want to think too hard in doing the math.
Let's say the poor person in my example is making $30,000 a year. (I know, a lot of people make less than that - bear with me).
Gas is now $3.00 per gallon. So some quick math and that means that it's a percentage/ratio of .0001. Now, how does a Rich person experience that price of gas? Using the same percentage, that would be that if the rich person who makes say $100,000 a year, they would be spending $10 per gallon for gas!
Then, I thought, what if the numbers were reversed?
So for a rich person of $100,000.00 they are paying a .00003 percentage of their income on a gallon of gas. So how much would that be for the person making only $30,000? 90 cents!
Again, I'm not sure what my point is here, but this just puts things in perspective here for me - and I hope you too.
Thoughts?