"Four people" is an exaggeration intended to be humorous. The more straightforward way of saying it is: there is tremendous market demand right now for this skillset. This skillset is extraordinarily uncommon irrespective of the demand for it. Additionally, market conditions currently offer many independent, extraordinarily attractive options to individuals who possess this skillset. Three options, among many, include being a) extraordinarily highly compensated at a Fortune 500 firm which is capable of being arbitrarily generous to retain their services, b) using their skillset to found a startup, or c) forsaking full-time employment and instead consulting for numbers which would make your head spin. There exist other options, too. This means that the number of people in the (already small) hiring pool who are actually available for hire is even smaller than you would otherwise assume.

My advice about the landing pages is in more depth on my blog in multiple places, but basically, "Build a CMS to spit arbitrarily high numbers of landing pages out of some data source which you have and some templates. Iterate on the templates in a data-driven fashion." It's essentially as technically complex as the Rails 15 minute build-a-blog demo. For more elaboration, see blog.

Four people is just an exaggeration. He's saying there are very few people who are genuinely great at this stuff.