Tanga offers the Apple AirPort Extreme 802.11ac Wireless Base Station, model no. ME918LL/A, for $143.99 plus $4.99 for shipping. That's $20 below our January mention of a new unit and the lowest total price we've seen for a new base station. (It's a current low for a new one by $36.) It uses 802.11ac WiFi technology, which offers up to 40% faster transmissions than 802.11n.
Don't mind buying a refurb? Best Buy sells the refurbished base station for $119.99 with free shipping.