This depends on the industry. I work on industrial machine control software, and we spend a huge amount of time on tests. We have to for some parts (human safety crtitical), but other parts would just be expensive if they failed (loss of income for customers, and possibly damaged equipment).

The key to making this scalable is to make as few parts as possible critical, and make the potential bad outcomes as benign as possible. (This lets you go to a lower rating in whatever safety standard applies to your industry.) You still need tests for the less critical parts though, while downtime is better than injury, if you want to sell future machines to your customers you need to have a good track record. At least if you don't want to compete on cost.