Michelle Malkin is a conservative blogger and TV "personality" with a bachelors degree in English, while Paul Krugman is a nobel laureate in Economics. While both may have their biases, I would most certainly give the analyses put forth by the latter infinitely more weight than those of the former.
They didn't spend $600m on the website. That figure comes from an open service contract with CGI that predates the ACA by a considerable amount of time. The amount of the contract spent on developing the healthcare.gov site is estimated to be between $70m - $125m; still not cheap, but definitely not on the order of half a billion dollars.
What strikes me here is that Microsoft could potentially make more money selling "we won't sue you" certificates to [Novell] Linux users than the companies actually providing *real* support for said systems