I think this isn’t arguing that you should aim to have 10 (or 1!) high/paying clients, but rather that it is better to have 100 (or 1000) medium-paying clients

I think this isn’t arguing that you should aim to have 10 (or 1!) high/paying clients, but rather that it is better to have 100 (or 1000) medium-paying clients than 10,000 (or 1,000,000) low-paying (or free) clients, because you are likely to underestimate the marginal cost of a single client, and at higher rates, this marginal cost is more significant. If you have 100 medium-paying clients then losing 1 is not such a big hit to revenue. If you have some kind of dynamic pricing, it seems reasonably likely that you’ll get a power law for how much clients pay, and you’ll be worried about the biggest client leaving even if you have lots of others.