ZNGA's market cap was 10x in 2012, when they bought the location for the 340/sq foot mentioned in the article. They occupied 65% of the building, which is a good capacity to be at if you're planning on growing.

Regarding buy vs. rent, I think at the time it made sense, if they were planning on sticking around for 5+ years, given the price per square foot they paid and the fact that they would fill up the entire space.