Quick take
If hydrogen sulfide is confirmed in the well, whole-house oxidation/filtration often lands in the low-to-mid four figures before installation. If only hot water smells, diagnose the water heater before buying treatment.
Whole-house sulfur treatment
Air oxidation and regenerating media are common for confirmed hydrogen sulfide in source water. Price rises with flow and combined iron/manganese treatment.
Hot-water-only odor can be cheaper to fix
A water-heater anode or bacterial issue can mimic a whole-well sulfur problem. Correct diagnosis can save thousands.
Carbon polishing
Carbon may help residual odor but is often not the primary treatment for meaningful hydrogen sulfide loading.
Testing and maintenance
Source testing plus periodic media/backwash maintenance belongs in the ownership budget.