The sticker price on a used or refurbished softener can look attractive, and sometimes it is a good deal. The price you pay up front is only one piece. What pushes the total up or down is mostly hidden in the unit's age, its parts, and the work needed to make it run.
What lowers the price
A unit with a documented refurbishment, a control valve that is still supported, and resin that was replaced or serviced at a known point will hold its value better. Prices also fall when a seller is clearing stock, moving, or replacing a unit that worked fine. A working control head with clear programming options is usually worth more than a shell with an unknown history.
What pushes the total up
Older valves may need parts that are hard to find. A unit that was never serviced may need resin replacement or a new control soon after you install it. Plumbing fittings, a bypass valve, a drain connection, and an outlet can all add to the bill, and so can a permit if your area requires one. If you need to ship or haul the unit, transport can cost more than the discount you gained.
What to verify before you pay
Ask for the age, the model, and the service history in writing. Ask whether the resin has been replaced and, if so, when the seller says it was done. Ask what warranty, if any, covers the used unit and whether it covers parts only. Compare the total of the unit, the fittings, the delivery, and any service visit before you judge the deal, and use the same list for every option you consider.
Where a ratings check helps
Use the company ratings as a reference point. A used unit is easier to judge when you can compare it against a new option from a company with a documented warranty and a clear service record. The company ratings page is a reasonable place to start that comparison.