Asics Cumulus unisex socks are £4.99 (£3.50 for bigger sizes), you can also get 20% off your entire order with the code below. You have to pay £5 for click and collect but with this you also get a £5 voucher to spend instore. I bought a pair of £5 socks instore with this.
20% off code - 9100000000671
I have these socks. Really nice support in all the right places. They have quite a tight fit around your feet.
There loads of other good clearance deals on the site, including running trainers by the way.