You're confusing yourself.
That's one room of the several they had (4 session track rooms, the hackathon room, and the main floor with the vendor booths, food area, and main stage). There were about 2,000 participants who paid, not the 100 or so you see in the picture below. (some sessions were sparsely populated, while others, like Gavin's were standing room only).
Oh, and they each paid $300-$350 to be there. Did all 200K of yours pay that much? It was probably free, right?
You're comparing apples to oranges.
