How To Get Rid Of Black Marks On Back?

I am 27years old. During my teenage years i used to get lot of pimples on my back. Now the pimples have stopped completely, but i am left with lots of black marks on my back. I have tried cosmetic peels but that doesnot show much improvement. The marks are so many that laser treatment is going to be very costly. Is there any other cosmetic or surgical procedures that can help.