As for replacing the batteries on Power Tools such as cordless drills and such; a "trick" that I discovered is to look for special offers on a new item with batteries. That seems to really work out a lot during the holiday season.
I used a DeWalt 18v drill and saw combo pack for several years, and when the batteries started to fail I was able to find a new DeWalt drill with TWO (2) 18v batteries included, for about the same price as a single replacement battery.
So, I saved money on replacing the batteries, and now I also have an extra cordless drill. I love being able to drill with one, and then grab the other to drive a screw without having to stop and change bits!
I am not saying that the brand-name batteries are as good or better than the rebuild that PrimeCell offers (I don't know). But, if you're headed out to the local mega-hardware store to look for a new battery; check for a new tool-with-batteries first... if you catch the right sale, you can come out way ahead.