Hi! Thanks for your post and interest in Hero Lab.
The base Pathfinder game system (the one that you select with your purchase of Hero Lab) provides you with the Core Rulebook. Were you to add up the cost to buy everything available from Paizo within Hero Lab, yes it would be a high amount. However, it's important to keep in mind that you'd be purchasing content from over 100 books.
We offer a couple bundle deals that you might want to explore, like our Bestiary 1-3 bundle and our Classic Bundle (which includes both our Campaign Setting & Player Companion bundles). You can find
more info on the bundles here. Purchasing bundles will help offset the cost of purchasing over 100 books worth of content.
However, going all in is something that probably isn't necessary for the majority of users.
Keep in mind that you can use the Editor to create material as well. So, if there were only a few things from a given set of books that you used, you could build these yourself in the Editor rather than purchase the ready-made data set(s). For example, in the beginning I had a character that used content mostly from the core game, APG, and Ultimate Magic. So I purchased Hero Lab, APG & Ultimate Magic. For the few feats/items I used from other books, I worked with friends to get them made in the Editor. Then when I decided to treat myself, I would buy the package.
I hope that helps clarify things a bit.