Credit goes to reader Stefan for the following deal.
There is a Christmas sale going on for P51D, A-10C on DCS website:
DCS: A-10C WARTHOG – 60% (15.99 USD)
DCS: BLACK SHARK 2 – 40% (23.99 USD)
DCS: P-51D MUSTANG – 25% (29.99 USD)
I don’t think these activate on Steam.