I remember all this from many years ago when a digital camera was put up at a ridiculously cheap price on Kodak's website. Of course lots of people tried to buy it, and eventually the retailer decided to let those people have it for the low price (including me). The establishment of a contract to sell requires the seller to offer the item (invitation to treat), the potential buyer to offer to buy, and the seller to accept the offer. Also, there is no obligation to sell at the price stated if it is patently wrong, so even a Fender is obviously worth more than £0. There's generally an "E&OE" knocking about somewhere - errors and omissions excepted. Aha. https://www.theguardian.com/money/2002/feb/02/jobsandmoney is the Kodak story.