Amazon sometimes advertises very low prices for certain items, but when you go to check out, they insist that you sign up for Prime in order to buy that specific item, when you naturally assume because it's sold and delivered by Amazon, that you'd simply get free delivery, and just free delivery, if your total order including that low priced item was over £20 in value.... and that's what happened the first time I tried to buy these overshoes, when they were £2.99 - I removed it from my basket.... but a few days later, the Prime requirment disappeared... and that's when I bought the final pair (it was the "final pair" the first time too) while buying something else. Immediately after I'd checked out, Amazon hiked the price of these overshoes to £13 - they sneak in this transitory Prime requirement trickery when selling all sorts of absurdly low priced items. Haven't tried these out yet - I bet they're rubbish at keeping my feet any warmer.