Long time ago in a far away Galaxy I got interested about the Battlestar Galactica board game and eventually bought it (40 eur). I liked it very much, and eventually bought the DVD boxes of the series (100+ eur). Then… I also ended up buying the Pegasus Expansion (another 40 eur).
Total cost: close to 200 eur.
The fact that I had couple of friends paying too helped… but it was quite interesting to note how all this worked. I got interested about the game, then I had to see the movies, then I bought more stuff for the game…
One guy put it this way (it was about a Tolkien based game):
I watch the movie, I want to play the game, I read one of the books I want to play the game, I play the game, I want to watch the movies, or read the books. if our game group continues in this vain we will never stop playing.
Priceless in a long run.