Most plumbers charge a flat rate, not hourly, for this job. That rate usually covers removing the old system (if you have one), cutting into copper or PEX pipes, installing a bypass valve, and connecting the drain line. Always ask for an itemized quote.
Beware of hidden costs: permits (though rare for softeners), extra parts for unusual pipe layouts, or hauling away old equipment. Some companies charge an extra $50 to $100 for that. Pro tip: schedule your install in the spring or fall, when plumbers aren’t swamped with frozen pipes or AC repairs. You might get a better rate.