Compared to revenue it doesnt seem crazy either: at approx $150M in Q1-17, thats over $300k revenue per employee per year (if the revenue and headcount stays flat). Certainly there are many profitable companies at a ratio like that.
But for ad-fueled companies the bar to profitability and long term success is quite a bit higher:
Alphabet does about 4x that ($1.3M/employee/year) [0], and Facebook does even better ($1.8M/employee/year) [1][2].