Ocean Technology via Amazon offers the Unitek USB 3.0 to Gigabit Ethernet Adapter, model no. Y-3470, for $13.99. Coupon code "JTEUL5SV" cuts it to $6.02. Plus, Prime members bag free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $8.02.) That's tied with our January mention as the lowest total price we've seen. (It's the best now for any such adapter by $6.) It features data transfer speeds up to 5Gb/s.