The attraction of fusion is "free energy" in that hydrogen is plentiful (even deuterium is plentiful, tritium less so). Helium is not unlimited at least here on Earth and we're busy pissing away our supply on party balloons thanks to a US government decision to sell its strategic reserve in the 90s.
But a fusion plant is expensive. It costs money for the raw materials and the labour to build and maintain it such that the energy it produces--if it ever becomes economically viable, which is far from certain--will not be "free".
Computing power might be cheap but it's not free. An AI/robot won't be "free" in the same sense either. They'll cost money to build. Those resources will cost money.
Also, not all energy is the same. Plants that power the electrical grid are one thing. The energy required to hurtle a large metal object into space is something else. Fusion might work quite well for infrastructure but will it be made to work where we currently use kerosene and oxygen? That vehicle too costs money.