Again, it depends on what you’re buying. A small ion or cation exchanger in a water filter is much more affordable than a hefty water softening system. Industrial ion exchangers are even more expensive.
The average cost of a point-of-use IE filter is $25-$75, while the average cost of an IE water softener is $1,000-$1,500. IE softening resins last for 8-10 years, so the upfront investment is worthwhile.