Commanders and Comrades! Steam are offering, for a limited time, the Tiberium Wars, Kane's Wrath, Red Alert 3 and Tiberian Twilight titles at the knock down price of 2,49€ as part of their Winter Sale. The offer end on 4 January 2018, so you'll need to hurry but you've still got time to buy for Christmas! The offers are linked below.
The titles (except C&C4: TT) are compatible with
C&C:Online, so if you're looking for an affordable way to get online in those games, this is probably it. N.B. You need the Steam version of Tiberium Wars to play the Steam version of Kane's Wrath.