Ah, I see. So, in short, you can be forced to return an order, but that is only because the order was not made with a "legal" price [0], so no legal transaction has taken place, and all that happened was you sending the webshop money without cause, and they mistakenly sending you a product, which both must be returned upon request by the other party.

[0] a "legal" price is a price which the customer would expect for such a product. But in a shop advertising "up to 60% off", a 50% off TV would still be legal price, even if it is a price error.