How much mass is needed to support an astronaut in space?
We don't have any closed-loop environments in orbit, and ship consumables (food, air, water, tools ...) from Earth. ISS is designed for a permanent crew of 6, and weighs 450,000 kg. Much of that supports experiments; perhaps that could be traded for extra life support and reduced consumables, with astronauts spending most of their time operating the life support equipment instead of doing science. While that ignores the reason why the astronauts are there in the first place, it brings us closer to the essential "cost of an astronaut" compared to the current "cost of a scientific participant".
Astronauts consume about 30kg of consumables per day, 11 metric tonnes per year. If we assume a 20 year lifespan for the components of a fully-occupied ISS, they "consume" an additional 4 metric tonnes (450/(6*20) of space station. Ignore for now the much larger cost of frequent rotation back to Earth, training, ground support, etc. The cost of an astronaut is 15 tonnes per year.
Compared to Electronics in Orbit
An Ivy Bridge CPU contains 1.4 billion transistors, and thinned to 160 μm weighs 70 milligrams. A metric tonne of Ivy Bridge chips might prove useful for 5 years before succumbing to obsolescence (when it will be replaced by 30 times as many transistors with the same mass). Assume a thinsat design that is 7% Ivy Bridge density electronics by weight, 1.4 trillion transistors per kilogram launched. 5y * 15,000kg/y is 100,000 trillion transistors in orbit for the same launch cost as the astronaut, 1E17 transistors at 2013 densities, potentially doubling every year.