First of all, you should check how high the sodium level is in your supplied water. You should find this out somewhere on the internet, or directly inquire about the water values. Then you can calculate how the sodium level changes when you use a "salt" water softening system.
There are limit values here that should not be exceeded, or must not be exceeded, because a high sodium level in the water on the one hand causes a strange taste, and can also be harmful to people with high blood pressure and venous diseases, provided that the tap water is also used as drinking water.
Normally, hard water indicates that there is a lot of magnesium and calcium in the water, and little sodium. Soft water often has a lot of sodium. Mg and Ca colloquially cause the limescale that precipitates when the water is heated. These salt systems exchange the Mg and Ca cations for Na cations, which is why such systems are also called ion exchangers.
We have such a system, which reduces the water hardness from 21 to 4. And after the conversion, we are still far from the sodium limit value. We also cannot detect any difference in taste, as we also drink our tap water.
The system itself is designed for a household, costs about €70 in electricity per year, and uses about 75-100 kg of salt, which corresponds to about €30-50. In addition, there is the annual maintenance of the system, which we cannot yet quantify. The first offer from the manufacturer was outrageous: almost €300. The system itself has a market value of just under €2000. The technician even advised us during installation to perform the maintenance ourselves, as you only need to flush one pump.
We will look for a company that maintains our heating and pump.
Regarding living comfort, I can say: never again without one. It is a myth that you no longer have to clean, there is still enough limescale left :) But I cannot tolerate hard water and have skin irritations from it. For the last 13 years in Karlsruhe, I suffered after every shower. Now it is significantly better. Another aspect is that we use less detergent... which is not insignificant in terms of cost.
One more note: if your water connection is in the basement, and you are below the wastewater outlet, you urgently need a lifting station. In addition, the softening system must be equipped with an Aqua-Stop, otherwise your basement could flood. The manufacturer of our system proudly charges almost €600 for this, those rip-off artists... luckily we are not affected by this. Sellers often forget to mention it because it is a profitable additional business without many alternatives.
I hope I was able to help a bit :)