Startups are a business, and part of business is understanding what every cost is. Part of that is understanding what a "fully burdened" employee costs, it's well over what their salary is.

Understanding what's "normal" is tougher. TBH, "normal" is whatever you're burning if you aren't wasting money.

A decent WAG at how much money you need to keep a mid-level employee employed for a year is about $250k, it doesn't matter much where, but you might inflate that a bit for SF or NYC, and drop it a bit for Nowhere'sville, Nebraska. That's salary ($100k plus or minus), benefits, office space, administrative overhead, vacation, etc.

You'll want to earn more than that, on average, per employee per year, to be profitable.

It's useful in other algebraic ways to get a gauge on other company's burn rates, size, or needed revenue.

For example, your competitor might advertise that they have 200 employees. That means they operating a $50m/year business to break even. A reasonable target for basic sustainment and growth is $300k/employee/year so they'd need to be a $60m/year business to be growing.

Here's some real world examples:

   Company     - Revenue        - Employees - Average/employee/year
   Oracle Corp - $38.27b (2014) - 122,458   - $312,515
   Microsoft   - $86.83b (2014) - 128,076   - $677,956
   Facebook    - $7.87b  (2013) - 8,348     - $942,740
   Sony        - $66.12b (2014) - 140,900   - $469,268
   Google      - $59.83b (2013) - 55,030    - $1.09m
   Apple       - $182.8b (2014) - 98,000    - $1.87m
   Radio Shack - $4.473b (2010) - 36,400    - $122,884
   Amazon      - $74.45b (2013) - 132,600   - $561,463
   Lockheed    - $45.358 (2013) - 116,000   - $391,017
   Boeing      - $86.623 (2013) - 168,421   - $514,324
   Leidos      - $7b (prj 2014) - 22,000    - $318,181
   SAIC        - $3.8b          - 13,000    - $292,307
   Tesla       - $2b     (2013) - 10,000    - $200,000
   Ford        - $147b   (2013) - 181,000   - $812,154
   Nokia       - $15,85b (2013) - 55,025    - $288,050
   

Now look down this list and think about who's considered wildly successful and hot and who's considered on the way out, in the doldrums or has had recent sell-offs or splits in the company. This isn't perfectly scientific, just a guideline.

Startups have a slight advantage in that you can sometimes hire employees at a lower salary in exchange for options. This can temporarily deflate the costs and let you beat these guidelines for a while. But ultimately you'll run out of paper to give out and you'll have to start paying people what they're worth.

However, Startup founders, especially first timers, are often at a disadvantage because they've never had to handle so much money before. One startup I was at had a changeover in CEOs and an analysis of non-employee expenses under the previous CEO showed a $30k/mo travel expense for him and the CTO.

Turns out the previous CEO and CTO were doing all their business traveling for sales in business class. We had been chronically understaffed. The new CEO cut the travel and hired an outside and inside sales-person for about the same and revenue started increasing shortly thereafter. Interoffice communications was turned into weekly phone conferences and communication even improved.

Don't spend your money in stupid ways and you'll have more to put behind the business.