Many companies offer 12-month interest-free financing if you buy through them. This can turn a $2,500 bill into $200 a month, which feels like a cup of coffee a day. Just ensure the interest rate after the promotion is not predatory.
If you see a deal for a $499 installed water softener, run the other way. These are often leased units with high monthly fees or ancient refurbished models that will break in a year. You pay for what you get, and cheap plumbing is rarely cheap in the long run.
Fun fact: The Romans used a primitive form of water softening by passing water through gravel and lime. We have come a long way, but we still pay for the luxury of clear glasses and silky hair. Some things never change.