Green Man Gaming offers Steam downloads of Sid Meier's Civilization VI for Windows, Mac, and Linux for $13.50. Coupon code "GMG12" cuts that to $11.88. (Fanatical ties this price via coupon code "FANATICAL10".) That's $6 under our July mention and the best deal we've seen. (It's the lowest price now by $3, and beats the Steam sale price by $6.) Deal ends January 10.
You don't even need an AARP membership card to qualify for the "senior" discounts at these stores.