That's the thing, this is not always true. It's true that generally you can throw money and hardware at a problem, but at some point you just reach the fundamental limit of the technology, at which point throwing money at the problem doesn't work.
In fact, being in a position where you can throw money at the problem is _brilliant_, as spending money is easy. So the point of _scalable_ technologies is to enable you to scale just by throwing money at the problem.
Case in point, at my old company we had this _massive_ Pg database running in RDS. It did not scale. Performance was terrible, and made the user experience shit. We were basically using the biggest instance size we could, with a few replicas powering read only endpoints. So at some point we migrated parts of it to Dynamo, and poof all of our problems went away, including operational ones.