I bought Chins 12-volt 200ah batteries for $600 each, and the 100ah batteries were $315 on Amazon. We have a Chins rep running a thread on the forums; here's the link:
Will, who created this board, did a teardown of the 100ah a few months back, great build, and performed as advertised. I'm certainly happy with mine. They don't have low temp shutdown, but that's not an issue for me.