A company easily spends 30%+ on taxes, benefits, stock options, etc for employees. The cost to a company is not just what the employee is paid directly.
So this puts it closer to $200K "salary" on average. For an engineering team in a tech company (not a car company, right?) $200K is pretty average today, including all the directors and managers.
Let's say I'm off the average pay is $150K. That's $225K a year spend by Tesla, That's still $113M a year, just on salaries for the people locating and designing new supercharger sites. Not including continuing maintenance, the land leases themselves, the construction, or the actual charger hardware. This BP spending $150M a year is way lower than Tesla was spending by a huge margin, maybe 8X. Which is good because Tesla was also delivering 15K points a year while BP thinks they can do 500, meaning Tesla was way more efficient.