I think we all forget that there aren't many carpet cleaning machines made. A piece of moulded plastic has to be made with tooling that can cost thousands to set up, so if the number produced is very small, the cost per finished item will be high.
You could buy a plastic bin for £1 in a cheapo shop, because there are millions of them made in the world.
£45 plus vat, the real cost of this item, is probably almost a non-profit sale for Alltec when you take everything into account. They're not Tesco, they haven't bough 5 million of them.