What you call the marginal rate is applied to the full salary as far as I know. And the social security is also applied to the full amount unless the person is employed by a Portuguese company that would pay half.
Even the most optimistic tax accountants say around 70% minimum is to be paid with various options applied. That would leave 24.000. Portugal has many loopholes of course, but the idea of the article or OP was that these loopholes are not needed or unfair. While I‘m saying they are needed or otherwise nobody would go there.
Now let me add that many nomads also have to pay into various things from their home countries. While there are double taxation agreements the story on health insurance and retirement funds and social security is much more complicated.
Unless you cut all ties to home you can come out with even less.