The biggest cost drivers are the volume of water, the category of water (clean, gray, or black), how long it sat, and how much material has to be removed and rebuilt. A clean-water spill caught in an hour is a fraction of the cost of a Category 3 sewage loss that sat overnight.
Mitigation and restoration are two phases. Mitigation stops the damage from spreading - extraction, drying, and antimicrobial treatment. Restoration is the rebuild back to pre-loss condition. Many losses need both, which is why the full range is wide.
Because most covered losses are paid by insurance minus your deductible, the more useful number is often your out-of-pocket cost, not the total invoice. A written, moisture-documented scope from a certified crew is what keeps the carrier paying the full, accurate amount.