I wonder how much of Pathfinder's sales are based upon the evangelical nature of its player base. I'm a system neutral type of guy. You can convince me to try out any system and there is a high chance that I'll find something about that system that I like. This also means that I tend to visit the forums for a bunch of games, and I definitely notice a change in tone between them.
There is definitely a core group of outspoken Pathfinder players who preach the Pathfinder way. While I'm not saying that they are a large percentage of Pathfinder players, they are extremely vocal. They will claim that 4th Edition abused their mother, killed their father and touched them in all the wrong places. The claim is usually that 4th Edition ruined D&D for them (a discussion for a different thread). This can best be demonstrated on the Piazo forums where a discussion was created about a high profile employee leaving WOTC. A overwhelming number of posts treated the man like he was the antichrist.
So I personally see the number of sales from Pathfinder attributed to the fans pushing the games into the hands of people. I know that for a new player to RPGs or 4th Edition, I wouldn't tell them to buy any of the books. I'd let them borrow a copy of my Rules Compendium or Player's Handbook and suggest that they get DDI for a month and build a few characters. If they took the time to create a character at Level X, X+1 and X+2, likely this would last them quite a few months in a bi-weekly campaign.
I feel that the number of hardcover sales by Paizo is generated by the fact that new players will be told that they need the books to play. I know that this is the case with Star Wars Saga Edition. While I love the system, I feel that the players will need the various books to level up their characters. While there are some computer related solutions for both Pathfinder and SWSE, I hardly believe that the sales of Heroforge + Pathfinder would be anywhere as large as DDI.