Real numbers would be interesting
For a start the Falcon 9 first stage has to leave fuel unburnt to power it's descent. That's fuel not available to boost the second stage higher, or to put it another way is mass taken off the rest of the payload. You end up with a much bigger, and hence more expensive, launcher than a non-reusable one for the same payload.
Then there's the reusability issue. Engines, pumps etc engineered for multiple use are going to be more expensive and probably heavier than one-shot equivalents, and (as the article says) will need a lot of expensive inspection and refurbishment between launches to ensure they're as reliable as new ones.
I'm not saying the economics won't make sense, just that it's not a given that reusable=cheaper. If an article is going to call itself "analysis" then I suggest it needs some facts and figures to back up its "slashing costs" claim.