I'm not surprised. I also imagine that they are looking at how many they can sell so it is profitable. With my car it is important to keep it as close to stock as possible. I do not know how many other makes used the same battery where they also want to keep it stock but I imagine the number it to be small.
If you buy one that needs to be shipped, make sure it is dry. I bought a used on here on turbo-buick.com However, he emailed and said there would be a delay because he had to drain the acid from the battery to avoid a hazardous material manifest. After attempting to drain thru the top, he proposed drilling holes in it. That is the last I heard and that was fine with me (I understand you can rehabilitate a used battery because the failure is a buildup of sludge (PbSO4 ???) that shorts out the plates which can be removed. If you want to contact him to see if he still has it, I can look up his contact info.