It looks like the entire Total War series, excluding STW and MTW, is currently on sale on Steam. Check out the deals on the Sega Collection sale page:
http://store.steampowered.com/sub/15550/
The entire pack itself is of questionable value, but it includes the following TW game sales (prices in USD):
RTW Gold: $6
RTW Alexander: $3
M2TW: $6
M2TW Kingdoms: $3
ETW: $12 (with DLCs for $2)
ETW Warpath: $6
NTW: $12 (with DLCs for $2 and $6)
...