Cost is driven by how much contaminated material must be removed and disposed of, the square footage affected, and how long the sewage sat. A backup caught early on a hard-surface floor is far cheaper than one that soaked into a finished basement overnight.
Because sewage is a biohazard, the price includes PPE, extraction, disposal, and antimicrobial treatment that a general cleanup does not - this is not a DIY-priced job.
If you carry a sewer or water-backup endorsement, most of this is covered up to your limit. Heartland provides a free assessment and adjuster-ready documentation so the claim reflects the real scope.