Wow. I tried to explain this earlier. Let me try again.
1.00 in 1980 is worth 2.83 today.
So say you invest 10,000.00 in 1980 and in 2013, you sell it for 28,300.00.
You DIDN'T ACTUALLY MAKE ANYTHING. What you sold it for is exactly what you paid for it in REAL inflation adjusted dollars. But you will pay capital gains tax on 18,300.00 that you "profited". The profit, however, is nothing but inflation. You will pay 15% of 18,300 for a total of $2,745.00. How did you make out really? You lost $2,745.00 is what really happened because what you're left with is 28,300 - 2745 = 25,555 and in 1980 dollars, that's only worth 9,017.00. You would have broken even except that the tax you paid on the gains you didn't really make caused you to lose about 10% of the real value of your invested wealth.
Remember, you sold for 28,300. In order to buy your "investment" today, that's what it would cost you. You can't turn around and re-buy that investment with the proceeds of your sale because you LOST MONEY since you got taxed for profit you DIDN'T REALLY MAKE.
I don't know if you get it or not at this point, but if you don't, then I'm not going to be able to teach you about this. If you still don't get it, then you should probably try to research and understand how inflation affects money and investments.