I think they meant if you didn't have a relevant bachelor's to go straight into the masters. Given we can't predict which bachelor's (or master's for that matter) is going to be rendered completely obsolete by technology, it's a valid concern. You wont necessarily be able to use your BS in CS to just immediately hop into an MBA program.

Given that, it's still not going to cost $1 million for a BS + MS. Even taking 8 years for both, you're looking at around $800k at the most expensive programs and those are rarely worth entertaining when very good and affordable state programs exist for half or even a tenth the cost.

Opportunity cost for a tech worker to learn something new from scratch?

If your old job is gone, your opportunity cost is not your old salary, it's your potential new salary. Likely a lot less.