There are plenty of tips in this guide that should help you to improve the efficiency of your water softener and cut down on your salt spend. You may also find that bulk-buying batches of salt can save you money. Manufacturers will often offer discounts on bigger up-front spends, so you’d pay less per bag for 3 bags of salt than you would for 1 bag, for instance.
Unfortunately, water softeners simply can’t operate without salt, so while you might be able to reduce your salt usage, you’ll always need to put aside some money for this maintenance task.