The parent clarifies above that they are not a home user.

Even if you believed they were a home user, they clearly demonstrated in their original comment that they did know that it was for long-term, high volume storage, and they did know the cost, and you appeared still to belittle them for not knowing.

It's a question in the sense of - why did you choose to say it in this way, which seemed impolite? What did you intend your comment to add?