The point was that the author was misleading in relating the prohibitive cost of labor to paychecks (you do the same). What made jobs prohibitively expensive in such a short period of time was another cost component, namely, health-care benefits.
In the context of your example, $40,000 job cost previously $60,000 when benefits were included, but now it is a greater amount.
Finally, the computation you offered is incorrect. Capital and labor are generally nonadditive. If one hopes to get $100,000 by investing $1M in a machine that requires labor input of $40,000/year, not hiring an employee today does NOT incur the opportunity cost you indicated: the capital is a sunk cost (possibly nonsalvagable), and what is forgone is the cash flow of $60,000/year (100,000 - 40,000). It is misleading to seek an equivalent capital and compare it to risk-free return.
There is no return today. Says more about hidden regulatory and potential liability costs-of which your argument concerning bennies is a relevant part of. I happen to be an employer...10years ago with 17-currently with 5...and I only see potentially going lower.
The employer has a bullseye on their back.