Am I missing something?
 

According to the Irish Rail website, these are the prices of annual tickets

Iarnród Éireann €2,950
Iarnród Éireann & Bus Éireann €3,290
Iarnród Éireann & Dublin Bus €3,190
All CIE Services €3,880


So for Bus Eireann, the supplement is €340, for Dublin Bus it is €240, but for both it is €930.

Are there additional CIE services that I am unaware of?

It's EUR135 more for a Dublin commuter Rail& Bus than an annual rail
then it's an extra 470 euros for the luas on top of these....

or if you just want Train and Luas it's EUR345 more...
I suppose it's the great tram network...

It may be down to patterns of usage. People that use "All CIE Services" may genuinely be doing a lot more travel than people using only say "Iarnród Éireann & Dublin Bus" (who in reality are likely to be doing XXXX-Dublin and back and using the bus to get to their final desination).

People using "All CIE Services" might being doing Bantry - Cork - Dublin and then to their final desination. I pity the commute though. :D

doesn't explain the luas cost though Victor...