I would definitely try to clean them before spending $100 or so dollars on new ones. Ive heard the toothpaste method works and if not you can try wet sanding it with high grit sandpaper and buffing it.
I've never personally done it, but I have heard of it working for many people. Apparently you get plain white toothpaste( not gel or colored kind, just solid plain white) and you apply it with a dry soft cloth and rub in a circular motion and it is supposed to remove all the grime and stuff and clear them up and when its all cleared you just use water and wash them off.
Like I said I have never tried it, but have heard it works.