I think the idea is that one only needs a single set of core books per group. Mind you, it is my experience that this is the case for all games; I've only ever heard of all players within a group purchasing the rulebooks in relation to D&D, and even then only as anecdotes on the internet. Anyway, the cards and various props are designed to minimize the necessity for rulebooks at the table, as all the relevant rules will be laid out before you.
One core set, and that's all you need to play the game. $100 dollars is a steep price for an RPG, yes, but you only really need spend it once for the whole group, which means the cost can be shared, and what you get in return for your money is style; You get production values and ease-of-use. Fantasy Flight put a lot of work into this game, and it has the price-tag to match, but considering the amount of content it doesn't strike me as being too overpriced for what you get. $100 is too much to spend if you're not certain you'll enjoy it, which I'll admit is unfortunate, but as I said, one can always try to share the cost.
I think it probably prudent not to look at the Adventurer's Kit as a $30 buy-in to the game; Look at it as a $30 indulgence for those of us who like to have their character sheets look pretty and official. One is by no means required to purchase it in order to play the game, when you can just do it the old fashion pencil-and-a-notepad way; It's just there to look nice. They threw some extra careers in there as additional incentive.