The simple explanation does not factor in economies of scale. You might make a good wage working for someone else because they have some kind of market advantage. Would 100 mini-Googles that were 1/100th the size of Google make as much money? No, because their advantage (at least in selling ads) has to do with the fact that they have such a high percentage of the inventory.
I'm not saying some hackers can't make more than their salary's worth by going alone, but the argument is way too simplified to account for the real world.
I agree. A huge corporation also has the structure in place in all levels that makes a programmer profitable from the beginning.
When starting a startup, you need to build that structure from scratch - from the marketing, to the sales process, to the scalability, support, hiring, etc. The reason why most employees think they're more than they're worth is because they don't see all the things that happened before they were hired, and all the things that happens behind the scenes that makes their specific tasks valuable to the company.
I'm not saying some hackers can't make more than their salary's worth by going alone, but the argument is way too simplified to account for the real world.