Energy is not cheaper on earth. Solar in space gets 24/7 power at a 30%+ rate vs the surface. Radiative cooling is passive and cheaper because there are no HVACs or chillers and high temperature chips reduce the need. The ISS does this already. Radiation really isn't a big issue with ECC and redundancy and optical links are fine for batch training.

The only hard part making the math work is the launch cost. They need reusable and reliable starship economics. If they hit that goal, it will become cheaper for pre-training, which is 70%+ of the budget for the frontier models.