I don't mean to crash this thread, but felt I should speak up.
Clay is all over the world, but detailing clay is not clay so to speak. To my knowledge, it is man-made from polybutene (a plastic resin) and abrasives, such as silica and ceramics, giving it a clay-like appearance and feel. All US-made detailing clay is covered by a
patent, which, I assume, contributes to some of the cost.
All that being said, I have heard plenty of stories of improperly made clay bars (from places like ebay) causing
significant marring or worse. I hope this isn't the case and you guys have found a great and affordable product. Just keep it in mind and always test in an inconspicuous area first. Personally, I'll be sticking to name brands.