$37M in sales/marketing to generate $47M in revenue in first 6 months of 2014. Are there metrics for Sales and Marketing expenses for a SAAS company that could be used for comparison? Seems pretty high, but maybe ok for a fast growing startup.
I don't know if you can draw a conclusion from those numbers alone, but it's typical for a SaaS business to measure Customer Acquisition Cost (CAC) and Lifetime Value (LTV) of the typical customer. Sales and marketing seem to be the majority of the CAC, but you can't tell the LTV from revenue numbers alone.
A rule of thumb is that $1 in sales/marketing expense should get you at least $1 in additional gross profit over the next 12 months. Depending on how much of that $47M was new revenue, it sounds like they're in decent shape on that score.
Although I don't know this for a fact, I would assume their free tier is considered part of their sales/marketing expense which may have something to do with that.