You think that top software engineering graduates in New York City make $26k per year? Recalibrate! Recalibrate!
I think the number you're looking for is "less than 4%". Remember that the office-construction expenses can be massaged by accountants to reduce taxes on them, and that an employee's (e.g.) $80k salary costs the employer considerably more than $80k, thanks to the employer share of things like Social Security and health insurance. To say nothing of the costs of recruiting a single employee. Note that a headhunter will charge you a cool $30k to recruit an employee with a $100k salary:
http://www.asktheheadhunter.com/basics2.htm
...and who knows what kind of stiff that headhunter is going to try to foist off on you?
The chances that the $4k per employee per year is paying off for Fog Creek are much, much better than you think.