I was at the Apple store the other day, just checking in. I have never seen an Apple store have a sale, but they had a table set out with a bunch of marked down merchandise on it. Half was third party products that were either outdated or previously opened, but there was definitely a fair share of Apple hardware marked down. Most of the markdown we between 20 and 30 percent.
However, there was a stack of airport express' that my fiance started looking through. In the middle of them was a box that said 15" ALU Powerbook Battery. All the airport express's were packaged in the same size box as well, so it wasn't easy to spot. The markdown? $70. Which brought the total price to only $50! I have never priced powerbook batteries before, but I knew that had to be a good deal.
I questioned the representative who said that it might be a return or just an old stock, but if anything was wrong with it or it didn't work out, just bring it back and they would exchange it for another one off the shelf.
I was shocked. The battery was brand new and it lasts about 30 minutes longer than my original one.
I'd really suggest going to your local Apple store and looking through their sale table.