I knew something like that would come up, hence my use of "almost".

But I actually disagree with your example. I was expecting something like Dollar Shave Club to be used as a counterexample, where the entire value is arguably produced by marketing.

While I don't have metrics (and it is hard to even define a good metric to distinguish the leverage produced by marketing vs. excellent product development when they exist since day 1), I seriously doubt even Apple's 1984 ad had superlinear boost relative to the $ invested on it the ad had the product engineering was not good enough to sell itself.

In fact, I am not sure if it is fair to say the original Mac is an astounding commercial success relative to other computers at its time, unlike Apple II. I feel the ad was famous for its artistic value and post-hoc success of Apple, not much because it actually sold the product.

But back to the primary discussion, think about it this way: had Mac not been a revolutionary product that carried its weight, would that ad even meant anything? As in could you even sensibly run that ad for any product and expect good performance? (This is especially relevant since the ad is pretty abstract and non-product specific, so it is not crazy to imagine this hypothetical scenario.)

Good grief. The entire premise was that owning a Mac made you different, unique. People bought the thing because they identified with THAT not because of specs. How do I know this? Because everyone remembers the commercial and how it made them feel and almost no one remembers the machine and what it did comparative to other options at the time.

You have conflated cause and effect here so much it is hard to untangle just where you diverged from reality, but the 1984 ad was not as important as you think. It ran once. Once. It became important as an icon later, but "everyone" doesn't remember how the commercial made them feel because most of them didn't see it. The Mac was, at the time, such a marvel of hardware and software engineering and so radically different than what was available at the time that it almost sold itself. You probably could not have picked a worse example to try to make the sales vs engineering case.

The original Mac was actually not a very useful product; 128K of memory was enough to get a taste of the graphic user interface, but not enough to do much in the way of useful work. There was a flurry of initial sales to early adopters on the basis of the marketing, the potential, then it fell off. Sales only picked up again when the memory was increased to 512K. That tends to get forgotten nowadays because of what happened afterwards, but it's not at all the case that the original Mac sold itself based on its capabilities as a product.