Unless he's talking about the same project in both cases, it's a meaningless comparison. Can you take that OSS dev and put them in the consulting firm and have them replace everyone else in terms of productivity? I worked in an enterprise software company with a couple of people who founded some very well known and widely adopted OSS components, and while they were great by all accounts, they weren't 500x developers, or indeed even 10x. The difference is that with the OSS projects, they could do whatever they liked.