Good post, and well done for finding the numbers. However the point of Mars Direct was to avoid some of the endlessly-extrapolating-upwards budget numbers by a

Good post, and well done for finding the numbers. However the point of Mars Direct was to avoid some of the endlessly-extrapolating-upwards budget numbers by avoiding big technology developments (building a giant ship in orbit / launching from a moonbase / exotic engine technology); making use of elements present on Mars to produce rocket fuel on-planet from a smaller feedstock sent from Earth; and making use of automation, by preceding each manned trip with an unmanned fuel-production vehicle, with there always being one more lot of return fuel than human crews on Mars. I quite agree with "beyond non state actors" - much of the above appears in Mars One's plans, probably because it's the only way they could even start to appear plausible on a below-shoestring budget. But for a state actor, or at least for the USA or some as-yet-unbuilt alliance of developed countries, Mars is possible with 80s technology, at a viable price. You don't need to multiply the numbers up forever, so long as you resist distracting proposals from those who in reality want funding for a moonbase, or nuclear rockets, or whatever other technologies that promise first you have to solve a difficult, expensive problem, then Mars is cheap and easy.