12k Delta Miles Roundtrip to Mexico Instead of 35k

Delta has put many routes between the US and Mexico on "sale" right now. I say "sale" because Delta doesn't have a published award chart anymore, but we know from charts maintained by people like us online that the standard lowest level US > Mexico award price is 17,500 Delta miles one way. Right now many routes are only 12,000 SkyMiles roundtrip.