Yes, If you like EIA and you hope to play it by mail, you have to buy it :).
Why, simply because no compagny in the world will pay developpement of a game with a so short perspective of winning money :).
Be realistic, who play EIA, not so much people.
I suspect that EIA matrix wasn't a real project, except for Monadman.
Actually he have build a first release of this game, as we all know it isn't completly finish, but as we bought it, play and test it, the game become better and better, and Matrix get money so Monadman and other guy can work on it.
For playing against AI : for I, it seem crazy, how can you play diplo against computer, maybe dealing memory upgrad for sweden :). So EIA is only a 7 humans game, and it's one of the best diplomatic game actually made.
We have to wait fully stable game and after maybe more option (Italian kingdown and other, dominat status for prussia, austria,...)
After maybe, some possibility to play via IP.
And later better AI maybe... But having a good AI for diplomatic game is a realy big work and certainly more, for a not so good AI at last...
So if you like EIA boardgame, YES you have to buy EIA computer game :).