is there a strong argument why spending 80000 hours in a job for jobs sake is ethically superior to selling enough time to meet ones need and using rest for ones own goals?

To give a more direct answer, "a job for jobs sake" sounds like a lost purpose. In harder times, everyone had to work hard for as many years as they could, to support themselves, their household, and their community, and the community couldn't afford many passengers. Having broken free of the Malthusian wolves, the pressure is off, but the attitudes remain: idleness is sinful.

And then again, from the transhumanist point of view, the pressure isn't off at all, it's been replaced by a different one. We now have the prospect of a whole universe to conquer. How many passengers can the human race afford in that enterprise, among those able to contribute to it?