YouBuyRite via eBay offers the refurbished No-Contract Apple iPhone 6 Plus 16GB Smartphone for AT&T in Space Gray, model no. MGAL2LL/A, or Silver, model no. MGAM2LL/A, for $299.99 with free shipping. That's $115 under our June mention and the lowest total price we've seen for this no-contract AT&T-locked 16GB phone. (It's also the best price we could find for a refurb now by $72.)
No warranty information is provided. Note that this phone may show minimal signs of use on the screen and light imperfections on the sides and/or back.