This is a simplification to make the calculation more straightforward. But a typical US workplace honors about 11 to 13 federal holidays. I assume that an AI does not need a vacation, but can't work 2 days straight autonomously when its human handlers are enjoying a weekend.

I took it as a napkin rounding of 365/7 because that’s the floor you pay an employee regardless of vacation time (in places like my country you’d add an extra month plus the prorated amount based on how many vacation days the employee has), so, not that people work 50 weeks per year, it’s just a reasonable approximation of what the cost the hiring company.

Looks like standard USA?