We already have constructed two other sites. One of them is +200m under granite mountains and it's already been constructed. Two or three days before the Israeli attack, Iran had officially announced that it would start enrichment in a third nuclear site at an undisclosed location in response to the biased IAEA report against our nuclear activities. So, we just need to install our centrifuges there.
Sure, the damage is serious. You have destroyed deuterium production, green salt and yellow cake production, uranium metal conversion, etc. But we don't need north of $500 billion dollars to restart. Some critical components like the centrifuge assembly center and the FEP at Natanz were underground and we don't know much about what has happened to them at this point. As for Fordow, If only the ventilation system of Fordow has been hit, the site can be repaired and become operational again. There are too many unknowns to know how long or how much it takes for Iran to repair the damages.