The transformer link should be in bold across the top and offered as a "people also bought" or "you may need this too" since I just spent two weeks waiting to finally receive my battery just to not be able to plug it in.
The battery and transformer ultimately add up to ~$80. I can see it being less expensive if you have more batteries to charge, and only need one charge cord to share. I decided to go this route instead of buying rechargeable AAAs and replacing them all the time. I hope I made the right choice."