If there are benefits (as most $40k jobs would have), then the cost to the company is probably at least twice the gross salary. For example, I know that my employer's cost/hour for me is twice the hourly rate that shows up on my paycheck -- and my organization was purposely set up to be on the low end of the cost/hour scale.
There are a lot of variables, but anywhere from 20-30% more than the stated "salary" is a decent rule of thumb as to the actual cost to a company of an employee. I've been self-employed since the late 80's, but the last time I had a look at my line in a personnel budget, my salary was $60,000. My line in the budget was $73,000 and change. So I was making $73,000 and change.
Michael