Urban office leasing is almost universally quoted by yearly rates (for whatever reason), but your parent poster quoted by the month instead.
$60/sf/yr works out to $5/sf/month, not far from your parent poster's assertion.
Re:The Open-Office Trap
by knowaveragejoe on Wednesday December 03, 2014 @06:41PM
(#8697066)
$60/sf by the above poster's metric(monthly) would be insanity.
I think you're off by quite a bit with your price-per-square-foot estimates: http://therealdeal.com/blog/2013/10/01/manhattan-leasing-str...
That is from last year and the average price in Manhattan was about $60/sf.