Our society / societies may well be able to afford to build this quantity of software well. We choose not to.
Just "my hunch", but one I reflect on a lot these days.
But this incredibly hypothetical. A lot of software labor today revolving around manipulating the user rather than aiding them so where we'd go with "better" versions of this is hard to say.
Oh! I thought you were going to say "testing teams, design reviewers, trainers".
I'm not on-board with this "10-50x" claim for the amount of effort. I'd say maybe 3x the effort, given the developers have been well-trained, the methodology is sound, and the managers' focus is exclusively quality. That last item is one I've never experienced; the closest I came was on a banking project where the entire development team was subordinated to the Head of Testing.
Getting everybody (or even a minority of any sufficient size) to act in service to a single goal has been a problem for humanity ever since we first invented society.